If it boots with one disk, but not the other, I would assume that points to some issue with the disk. Did you set up the "other" disk independently or did you "clone"/dd it from the fully set up "first" disk? I'm not sure if I wanted to do that, or if you even can do that.
Initially I created the two disks separately, both from the original image. It could boot successfully. I changed a few things, after that it didn't boot anymore with two disks.
After several unsuccessful attempts I rewrote it with the original image (didn't help), and also tried cloning (dd) the partitions (didn't help neither) on the second disk. What I didn't try (but definitely will) is to boot with this disk alone, make the necessary changes, and see if it's working as root disk (slot B / left).
I'm not sure if it was clear... In short: I'll try everyhing... 
The two disk, and the partitions on them have the same uuid (I mean, in pairs: sda1=sdb1, sda2=sdb2). Isn't it a problem? Is there any mechanism based on uuid (in boot process, or in mounting filesystems, or in changing data on filesystems)?
I'm a bit stumped. It might be something you did to the configuration that breaks something once it finds the second disk. I don't know, serial output will most probably tell you right away what's wrong.
fstab, at least by default, mounts partitions using UUIDs. For that reason alone I would want at least the data partitions to have different UUIDs. (It's natural that sdx1 and sdx2 have the same UUIDs, they are all cloned from the same image after all, but obviously they get mounted by their device name.)
Well... I attached a serial cable to see the logs.
It seems that it's not the disk causing the error. The last lines are:
[ 4.738493] urandom-seed: Seeding with /etc/urandom.seed
[ 4.771441] procd: - early -
[ 4.774422] procd: - watchdog -
[ 5.317011] procd: - watchdog -
[ 5.321765] procd: - ubus -
And then reboot.
Here is the full log:
U-Boot 2009.08-svn54115 (Nov 15 2011 - 10:54:56), Build: 0.0.12
CPU: AMCC PowerPC 4APM82181 Rev. E at 800 MHz (PLB=200, OPB=100, EBC=100 MHz)
Security support
Bootstrap Option E - Boot ROM Location NOR/SRAM (8 bits)
32 kB I-Cache 32 kB D-Cache
Board: Apollo-3G - APM82181 Board, 2*SATA, 1*USB
I2C: ready
DRAM: Auto calibration - \|/-\|/-\ \|/-\|/-\256 MB
FLASH: 512 kB
DTT: 1 FAILED INIT
Net: PHY EC1 Register: 0x2c8c
ppc_4xx_eth0
Type run flash_nfs to mount root filesystem over NFS
e[44me[37mp=============================================================================q
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|:::::::::::WWWWWWWWW::::WWWWWWW::::::::WWWWWWW::DDDDDDDDDDDDDDDDD::::::::::::|
|:::::::::::WWWWWWWW::::WWWWWWWW:::::::WWWWWWW::DDDDDDDDDDDDDDDDDDDD::::::::::|
|:::::::::::WWWWWWWW:::WWWWWWWWW::::::WWWWWWW::DDDDDDDDDDDDDDDDDDDDDD:::::::::|
|::::::::::::::::::::::::::::::::::::::::::::::::::::::::::DDDDDDDDDDD::::::::|
|:::::::::::WWWWWWW:::WWWWWWWWWW::::WWWWWWW::DDDDDDDDD:::::::DDDDDDDDD::::::::|
|:::::::::::WWWWWWW::WWWWWWWWWWW:::WWWWWWW::DDDDDDDDD::::::::DDDDDDDDD::::::::|
|:::::::::::WWWWWW::WWWWWW::WWWWW:WWWWWWW::DDDDDDDDDD:::::::DDDDDDDDDD::::::::|
|:::::::::::WWWWWWWWWWWWW:::WWWWWWWWWWWW::DDDDDDDDDD::::::DDDDDDDDDDD:::::::::|
|:::::::::::WWWWWWWWWWWW::::WWWWWWWWWWW::DDDDDDDDDDD:::DDDDDDDDDDDDD::::::::::|
|:::::::::::WWWWWWWWWWW:::::WWWWWWWWWW::DDDDDDDDDDDDDDDDDDDDDDDDDD::::::::::::|
|:::::::::::WWWWWWWWWW::::::WWWWWWWWW::DDDDDDDDDDDDDDDDDDDDDDDDD::::::::::::::|
|:::::::::::WWWWWWWWW:::::::WWWWWWWW::DDDDDDDDDDDDDDDDDDDDDDDD::::::::::::::::|
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b=============================================================================de[40m e[37m
Hit any key to stop autoboot: 1 0
USB: OTG-Controller ID(0x4F54) Version(0x290A)
Err detect usb time out hostport.d32 0x00001000
0 USB Device(s) found
scanning bus for storage devices...
0 Storage Device(s) found
** Block device usb 0 not supported
Board is not configured for test. Do normal boot.
----- Checking Boot Partitions -----
SATA DWC initialization 0
init: Waiting for device...
sata_dwc: Device found
scan: Waiting for device...
SATA DWC initialization 1
init: Waiting for device...
sata_dwc: Device found
scan: Waiting for device...
supports DRM functions and may not be fully accessable.
Loading file "/boot/boot.scr" from sata device 1:1 (hdb1)
624 bytes read
1:1
## Executing script at 00100000
SATA DWC initialization 0
init: Waiting for device...
sata_dwc: Device found
scan: Waiting for device...
SATA DWC initialization 1
init: Waiting for device...
sata_dwc: Device found
scan: Waiting for device...
supports DRM functions and may not be fully accessable.
Loading file "/boot/uImage" from sata device 1:1 (hdb1)
2738039 bytes read
Loading file "/boot/apollo3g.dtb" from sata device 1:1 (hdb1)
16384 bytes read
Loaded part 1
## Booting kernel from Legacy Image at 01000000 ...
Image Name: POWERPC OpenWrt Linux-4.14.50
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 2737975 Bytes = 2.6 MB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
## Flattened Device Tree blob at 01800000
Booting using the fdt blob at 0x1800000
Uncompressing Kernel Image ... OK
Loading Device Tree to 00ff9000, end 00ffffff ... OK
[ 0.000000] bootconsole [udbg0] enabled
[ 0.000000] Linux version 4.14.50 (buildbot@builds-03.infra.lede-project.org) (gcc version 7.3.0 (OpenWrt GCC 7.3.0 r6984-fa0275b)) #0 Fri Jun 22 10:22:57 2018
[ 0.000000] Using PowerPC 44x Platform machine description
[ 0.000000] Found legacy serial port 0 for /plb/opb/serial@ef600300
[ 0.000000] mem=4ef600300, taddr=4ef600300, irq=0, clk=7407407, speed=0
[ 0.000000] -----------------------------------------------------
[ 0.000000] phys_mem_size = 0x10000000
[ 0.000000] dcache_bsize = 0x20
[ 0.000000] icache_bsize = 0x20
[ 0.000000] cpu_features = 0x0000000010100040
[ 0.000000] possible = 0x0000000030100040
[ 0.000000] always = 0x0000000000100000
[ 0.000000] cpu_user_features = 0x8c008000 0x00000000
[ 0.000000] mmu_features = 0x00000008
[ 0.000000] -----------------------------------------------------
[ 0.000000] Top of RAM: 0x10000000, Total RAM: 0x10000000
[ 0.000000] Memory hole size: 0MB
[ 0.000000] Zone ranges:
[ 0.000000] DMA [mem 0x0000000000000000-0x000000000fffffff]
[ 0.000000] Normal empty
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000000000000-0x000000000fffffff]
[ 0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x000000000fffffff]
[ 0.000000] On node 0 totalpages: 65536
[ 0.000000] free_area_init_node: node 0, pgdat c055ba30, node_mem_map cfded000
[ 0.000000] DMA zone: 512 pages used for memmap
[ 0.000000] DMA zone: 0 pages reserved
[ 0.000000] DMA zone: 65536 pages, LIFO batch:15
[ 0.000000] MMU: Allocated 1088 bytes of context maps for 255 contexts
[ 0.000000] pcpu-alloc: s0 r0 d32768 u32768 alloc=1*32768
[ 0.000000] pcpu-alloc: [0] 0
[ 0.000000] Built 1 zonelists, mobility grouping on. Total pages: 65024
[ 0.000000] Kernel command line: root=/dev/sda2 rw rootfstype=ext4 console=ttyS0,115200
[ 0.000000] PID hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.000000] Dentry cache hash table entries: 32768 (order: 5, 131072 bytes)
[ 0.000000] Inode-cache hash table entries: 16384 (order: 4, 65536 bytes)
[ 0.000000] Memory: 253952K/262144K available (4584K kernel code, 208K rwdata, 572K rodata, 188K init, 243K bss, 8192K reserved, 0K cma-reserved)
[ 0.000000] Kernel virtual memory layout:
[ 0.000000] * 0xfffdf000..0xfffff000 : fixmap
[ 0.000000] * 0xfde00000..0xfe000000 : consistent mem
[ 0.000000] * 0xfde00000..0xfde00000 : early ioremap
[ 0.000000] * 0xd1000000..0xfde00000 : vmalloc & ioremap
[ 0.000000] SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[ 0.000000] NR_IRQS: 512, nr_irqs: 512, preallocated irqs: 16
[ 0.000000] UIC0 (32 IRQ sources) at DCR 0xc0
[ 0.000000] UIC1 (32 IRQ sources) at DCR 0xd0
[ 0.000000] UIC2 (32 IRQ sources) at DCR 0xe0
[ 0.000000] UIC3 (32 IRQ sources) at DCR 0xf0
[ 0.000000] time_init: decrementer frequency = 800.000008 MHz
[ 0.000000] time_init: processor frequency = 800.000008 MHz
[ 0.000015] clocksource: timebase: mask: 0xffffffffffffffff max_cycles: 0xb881274fa3, max_idle_ns: 440795210636 ns
[ 0.010284] clocksource: timebase mult[1400000] shift[24] registered
[ 0.016592] clockevent: decrementer mult[ccccccef] shift[32] cpu[0]
[ 0.022858] pid_max: default: 32768 minimum: 301
[ 0.027539] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.034064] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.044084] random: get_random_u32 called from 0xc01feab8 with crng_init=0
[ 0.051161] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 1911260446275000 ns
[ 0.060829] futex hash table entries: 256 (order: -1, 3072 bytes)
[ 0.067669] NET: Registered protocol family 16
[ 0.074264] PPC4XX OCM1: 32768 Bytes (enabled)
[ 0.078624] PPC4XX OCM1: 32768 Bytes (non-cached)
[ 0.083283] PPC4XX OCM1: 0 Bytes (cached)
[ 0.087318] debugfs ppc4xx ocm: failed to create file
[ 0.092450] 256k L2-cache enabled
[ 0.095766] PCIE0: Port disabled via device-tree
[ 0.100938] PCI: Probing PCI hardware
[ 0.113468] SCSI subsystem initialized
[ 0.117633] libata version 3.00 loaded.
[ 0.123020] clocksource: Switched to clocksource timebase
[ 0.128987] NET: Registered protocol family 2
[ 0.133730] TCP established hash table entries: 2048 (order: 1, 8192 bytes)
[ 0.140623] TCP bind hash table entries: 2048 (order: 1, 8192 bytes)
[ 0.146911] TCP: Hash tables configured (established 2048 bind 2048)
[ 0.153285] UDP hash table entries: 256 (order: 0, 4096 bytes)
[ 0.159040] UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
[ 0.165368] NET: Registered protocol family 1
[ 0.169668] PCI: CLS 0 bytes, default 32
[ 0.176291] dw_dmac 4bffd0800.dma: DesignWare DMA Controller, 2 channels
[ 0.187199] Crashlog allocated RAM at address 0x3f00000
[ 0.192872] workingset: timestamp_bits=30 max_order=16 bucket_order=0
[ 0.203267] squashfs: version 4.0 (2009/01/31) Phillip Lougher
[ 0.217986] io scheduler noop registered
[ 0.221831] io scheduler deadline registered (default)
[ 0.227204] GPIO line 472 (enable EMAC PHY) hogged as output/low
[ 0.233128] GPIO line 473 (Enable Reset Button, disable NOR) hogged as output/low
[ 0.240547] GPIO line 474 (Power USB Core) hogged as output/low
[ 0.246422] GPIO line 475 (Power Drive Port 1) hogged as output/low
[ 0.252643] GPIO line 479 (Power Drive Port 0) hogged as output/low
[ 0.259624] Serial: 8250/16550 driver, 16 ports, IRQ sharing enabled
[ 0.267636] console [ttyS0] disabled
\CA[ 0.291219] serial8250.0: ttyS0 at MMIO 0x4ef600300 (irq = 19, base_baud = 462962) is a U6_16550A
[ 0.300001] console [ttyS0] enabled
[ 0.300001] console [ttyS0] enabled
[ 0.306894] bootconsole [udbg0] disabled
[ 0.306894] bootconsole [udbg0] disabled
[ 0.315202] console [ttyS0] disabled
[ 0.318820] console [ttyS0] enabled
[ 0.322779] sata-dwc 4bffd1000.sata: id 0, controller version 1.91
[ 0.332723] scsi host0: sata-dwc
[ 0.336187] ata1: SATA max UDMA/133 irq 33
[ 0.340409] sata-dwc 4bffd1800.sata: id 0, controller version 1.91
[ 0.347536] scsi host1: sata-dwc
[ 0.350937] ata2: SATA max UDMA/133 irq 34
[ 0.355453] of-flash 4fff80000.nor_flash: do_map_probe() failed for type cfi_probe
[ 0.363666] of-flash 4fff80000.nor_flash: do_map_probe() failed
[ 0.370212] libphy: Fixed MDIO Bus: probed
[ 0.374310] PPC 4xx OCP EMAC driver, version 3.54
[ 0.379303] MAL v2 /plb/mcmal, 1 TX channels, 1 RX channels
[ 0.385059] RGMII /plb/opb/emac-rgmii@ef601500 initialized with MDIO support
[ 0.392204] TAH /plb/opb/emac-tah@ef601350 initialized
[ 0.397636] /plb/opb/emac-rgmii@ef601500: input 0 in rgmii mode
[ 0.403650] libphy: emac_mdio: probed
[ 0.519767] eth0: EMAC-0 /plb/opb/ethernet@ef600c00, MAC 00:90:a9:3d:80:c1
[ 0.526641] eth0: found Broadcom BCM50610 PHY (0x01)
[ 0.531671] i2c /dev entries driver
[ 0.535262] booke_wdt: powerpc book-e watchdog driver loaded
[ 0.541345] device-mapper: ioctl: 4.37.0-ioctl (2017-09-20) initialised: dm-devel@redhat.com
[ 0.552920] NET: Registered protocol family 10
[ 0.558864] Segment Routing with IPv6
[ 0.562610] NET: Registered protocol family 17
[ 0.567082] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this.
[ 0.579993] 8021q: 802.1Q VLAN Support v1.8
[ 0.685793] ata1: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
[ 0.694343] ata1.00: ATA-9: Samsung SSD 840 Series, DXT09B0Q, max UDMA/133
[ 0.701208] ata1.00: 234441648 sectors, multi 16: LBA48 NCQ (depth 1/32)
[ 0.710313] ata1.00: configured for UDMA/133
[ 0.714929] scsi 0:0:0:0: Direct-Access ATA Samsung SSD 840 9B0Q PQ: 0 ANSI: 5
[ 0.723079] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
[ 0.730093] ata1.00: Enabling discard_zeroes_data
[ 0.735561] sd 0:0:0:0: [sda] 234441648 512-byte logical blocks: (120 GB/112 GiB)
[ 0.743187] sd 0:0:0:0: [sda] Write Protect is off
[ 0.747977] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
[ 0.753051] ata2.00: supports DRM functions and may not be fully accessible
[ 0.760003] ata2.00: ATA-9: Samsung SSD 840 EVO 250GB, EXT0DB6Q, max UDMA/133
[ 0.767118] ata2.00: 488397168 sectors, multi 1: LBA48 NCQ (depth 1/32)
[ 0.773868] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[ 0.782882] sata-dwc 4bffd1800.sata: sata_dwc_isr: DMA not pending intpr=0x80000080 status=0x00000050 pending=0
[ 0.782917] sata-dwc 4bffd1800.sata: sata_dwc_clear_dmacr DMA protocol RX and TX DMA not pending tag=0x1f pending=0 dmacr: 0x00000006
[ 0.782923] sata-dwc 4bffd1800.sata: DMA not pending tag=0x1f pending=0
[ 0.782931] sata-dwc 4bffd1800.sata: sata_dwc_dma_xfer_complete DMA protocol RX and TX DMA not pending dmacr: 0x00000004
[ 0.822456] sata-dwc 4bffd1800.sata: sata_dwc_isr: DMA not pending intpr=0x80000080 status=0x00000050 pending=0
[ 0.832525] sata-dwc 4bffd1800.sata: sata_dwc_clear_dmacr DMA protocol RX and TX DMA not pending tag=0x1f pending=0 dmacr: 0x00000006
[ 0.844468] sata-dwc 4bffd1800.sata: DMA not pending tag=0x1f pending=0
[ 0.851052] sata-dwc 4bffd1800.sata: sata_dwc_dma_xfer_complete DMA protocol RX and TX DMA not pending dmacr: 0x00000004
[ 0.861976] sata-dwc 4bffd1800.sata: sata_dwc_isr: DMA not pending intpr=0x80000080 status=0x00000050 pending=0
[ 0.872042] sata-dwc 4bffd1800.sata: sata_dwc_clear_dmacr DMA protocol RX and TX DMA not pending tag=0x1f pending=0 dmacr: 0x00000006
[ 0.883988] sata-dwc 4bffd1800.sata: DMA not pending tag=0x1f pending=0
[ 0.890572] sata-dwc 4bffd1800.sata: sata_dwc_dma_xfer_complete DMA protocol RX and TX DMA not pending dmacr: 0x00000004
[ 0.901994] ata1.00: Enabling discard_zeroes_data
[ 0.906932] ata2.00: supports DRM functions and may not be fully accessible
[ 0.914278] sata-dwc 4bffd1800.sata: sata_dwc_isr: DMA not pending intpr=0x80000080 status=0x00000050 pending=0
[ 0.924357] sata-dwc 4bffd1800.sata: sata_dwc_clear_dmacr DMA protocol RX and TX DMA not pending tag=0x1f pending=0 dmacr: 0x00000006
[ 0.936303] sata-dwc 4bffd1800.sata: DMA not pending tag=0x1f pending=0
[ 0.942887] sata-dwc 4bffd1800.sata: sata_dwc_dma_xfer_complete DMA protocol RX and TX DMA not pending dmacr: 0x00000004
[ 0.953813] sata-dwc 4bffd1800.sata: sata_dwc_isr: DMA not pending intpr=0x80000080 status=0x00000050 pending=0
[ 0.963924] sata-dwc 4bffd1800.sata: sata_dwc_clear_dmacr DMA protocol RX and TX DMA not pending tag=0x1f pending=0 dmacr: 0x00000006
[ 0.975874] sata-dwc 4bffd1800.sata: DMA not pending tag=0x1f pending=0
[ 0.982458] sata-dwc 4bffd1800.sata: sata_dwc_dma_xfer_complete DMA protocol RX and TX DMA not pending dmacr: 0x00000004
[ 0.993408] sata-dwc 4bffd1800.sata: sata_dwc_isr: DMA not pending intpr=0x80000080 status=0x00000050 pending=0
[ 1.003516] sata-dwc 4bffd1800.sata: sata_dwc_clear_dmacr DMA protocol RX and TX DMA not pending tag=0x1f pending=0 dmacr: 0x00000006
[ 1.015463] sata-dwc 4bffd1800.sata: DMA not pending tag=0x1f pending=0
[ 1.022047] sata-dwc 4bffd1800.sata: sata_dwc_dma_xfer_complete DMA protocol RX and TX DMA not pending dmacr: 0x00000004
[ 1.032902] ata2.00: configured for UDMA/133
[ 1.037460] scsi 1:0:0:0: Direct-Access ATA Samsung SSD 840 DB6Q PQ: 0 ANSI: 5
[ 1.046567] sda: sda1 sda2 sda3
[ 1.050409] sd 1:0:0:0: [sdb] 488397168 512-byte logical blocks: (250 GB/233 GiB)
[ 1.058612] ata1.00: Enabling discard_zeroes_data
[ 1.063628] sd 1:0:0:0: [sdb] Write Protect is off
[ 1.068428] sd 1:0:0:0: [sdb] Mode Sense: 00 3a 00 00
[ 1.073973] sd 0:0:0:0: [sda] Attached SCSI disk
[ 1.078655] sd 1:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[ 1.089041] sdb: sdb1 sdb2 sdb3 sdb4
[ 1.093950] sd 1:0:0:0: [sdb] Attached SCSI disk
[ 1.098643] md: Waiting for all devices to be available before autodetect
[ 1.105416] md: If you don't use raid, use raid=noautodetect
[ 1.111451] md: Autodetecting RAID arrays.
[ 1.115558] md: autorun ...
[ 1.118348] md: ... autorun DONE.
[ 1.125507] EXT4-fs (sda2): warning: mounting unchecked fs, running e2fsck is recommended
[ 1.135417] EXT4-fs (sda2): mounted filesystem without journal. Opts: (null)
[ 1.142504] VFS: Mounted root (ext4 filesystem) on device 8:2.
[ 1.149105] Freeing unused kernel memory: 188K
[ 1.179642] init: Console is alive
[ 1.183205] init: - watchdog -
[ 1.206196] random: fast init done
[ 1.227511] kmodloader: loading kernel modules from /etc/modules-boot.d/*
[ 1.247503] usbcore: registered new interface driver usbfs
[ 1.253047] usbcore: registered new interface driver hub
[ 1.258419] usbcore: registered new device driver usb
[ 1.275070] usbcore: registered new interface driver usb-storage
[ 1.281449] kmodloader: done loading kernel modules from /etc/modules-boot.d/*
[ 1.298966] init: - preinit -
[ 1.416769] eth0: link is down
[ 1.420303] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 1.436889] random: procd: uninitialized urandom read (4 bytes read)
Press the [f] key and hit [enter] to enter failsafe mode
Press the [1], [2], [3] or [4] key and hit [enter] to select the debug level
[ 3.518253] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[ 4.520198] mount_root: mounting /dev/root
[ 4.526234] EXT4-fs (sda2): re-mounted. Opts: (null)
[ 4.531385] mount_root: loading kmods from internal overlay
[ 4.549144] kmodloader: loading kernel modules from //etc/modules-boot.d/*
[ 4.556862] kmodloader: done loading kernel modules from //etc/modules-boot.d/*
[ 4.684202] block: attempting to load /etc/config/fstab
[ 4.690718] block: extroot: not configured
[ 4.713917] EXT4-fs (sda1): warning: mounting unchecked fs, running e2fsck is recommended
[ 4.729622] EXT4-fs (sda1): mounted filesystem without journal. Opts: (null)
[ 4.738493] urandom-seed: Seeding with /etc/urandom.seed
[ 4.771441] procd: - early -
[ 4.774422] procd: - watchdog -
[ 5.317011] procd: - watchdog -
[ 5.321765] procd: - ubus -
U-Boot 2009.08-svn54115 (Nov 15 2011 - 10:54:56), Build: 0.0.12
CPU: AMCC PowerPC 4APM82181 Rev. E at 800 MHz (PLB=200, OPB=100, EBC=100 MHz)
Security support
Bootstrap Option E - Boot ROM Location NOR/SRAM (8 bits)
32 kB I-Cache 32 kB D-Cache
Board: Apollo-3G - APM82181 Board, 2*SATA, 1*USB
I2C: ready
DRAM: Auto calibration - \|/-\|/-\ \|/-\|/-\256 MB
FLASH: 512 kB
DTT: 1 FAILED INIT
Net: PHY EC1 Register: 0x2c8c
ppc_4xx_eth0
Type run flash_nfs to mount root filesystem over NFS
e[44me[37mp=============================================================================q
|:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::|
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|:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::|
|:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::|
|:::::::::::WWWWWWWWW::::WWWWWWW::::::::WWWWWWW::DDDDDDDDDDDDDDDDD::::::::::::|
|:::::::::::WWWWWWWW::::WWWWWWWW:::::::WWWWWWW::DDDDDDDDDDDDDDDDDDDD::::::::::|
|:::::::::::WWWWWWWW:::WWWWWWWWW::::::WWWWWWW::DDDDDDDDDDDDDDDDDDDDDD:::::::::|
|::::::::::::::::::::::::::::::::::::::::::::::::::::::::::DDDDDDDDDDD::::::::|
|:::::::::::WWWWWWW:::WWWWWWWWWW::::WWWWWWW::DDDDDDDDD:::::::DDDDDDDDD::::::::|
|:::::::::::WWWWWWW::WWWWWWWWWWW:::WWWWWWW::DDDDDDDDD::::::::DDDDDDDDD::::::::|
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b=============================================================================de[40m e[37m
Hit any key to stop autoboot: 1 0
USB: OTG-Controller ID(0x4F54) Version(0x290A)
In case of a normal boot (with only one disk attached) it looks like this:
[ 4.380061] procd: - early -
[ 4.383014] procd: - watchdog -
[ 4.921027] procd: - watchdog -
[ 4.924369] procd: - ubus -
[ 4.934441] random: ubusd: uninitialized urandom read (4 bytes read)
[ 4.978109] random: ubusd: uninitialized urandom read (4 bytes read)
[ 4.984740] random: ubusd: uninitialized urandom read (4 bytes read)
[ 4.991693] procd: - init -
Please press Enter to activate this console.
[ 5.115854] kmodloader: loading kernel modules from /etc/modules.d/*
[ 5.142509] ip6_tables: (C) 2000-2006 Netfilter Core Team
[ 5.159699] ip_tables: (C) 2000-2006 Netfilter Core Team
[ 5.171212] nf_conntrack version 0.5.0 (4096 buckets, 16384 max)
[ 5.205766] xt_time: kernel timezone is -0000
[ 5.215911] PPP generic driver version 2.4.2
[ 5.221750] NET: Registered protocol family 24
[ 5.228436] kmodloader: done loading kernel modules from /etc/modules.d/*
[ 6.432255] urandom_read: 5 callbacks suppressed
[ 6.432262] random: jshn: uninitialized urandom read (4 bytes read)
[ 8.272376] eth0: link is up, 1000 FDX, pause enabled
[ 8.277533] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 8.283384] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
I also did really extensive testing. I found that the Duo fails to boot if I change anything in the partition table on any disk.
That's really bad... This way it will not feasible to use as a NAS. 
The interesting part is not where it ends, but what happens in between. I compared it to a bootlog of two hard disks, and I find one interesting difference already before booting:
supports DRM functions and may not be fully accessable.
And later on, for each drive:
[ 0.782882] sata-dwc 4bffd1800.sata: sata_dwc_isr: DMA not pending intpr=0x80000080 status=0x00000050 pending=0
[ 0.782917] sata-dwc 4bffd1800.sata: sata_dwc_clear_dmacr DMA protocol RX and TX DMA not pending tag=0x1f pending=0 dmacr: 0x00000006
[ 0.782923] sata-dwc 4bffd1800.sata: DMA not pending tag=0x1f pending=0
[ 0.782931] sata-dwc 4bffd1800.sata: sata_dwc_dma_xfer_complete DMA protocol RX and TX DMA not pending dmacr: 0x00000004
[ 0.822456] sata-dwc 4bffd1800.sata: sata_dwc_isr: DMA not pending intpr=0x80000080 status=0x00000050 pending=0
[ 0.832525] sata-dwc 4bffd1800.sata: sata_dwc_clear_dmacr DMA protocol RX and TX DMA not pending tag=0x1f pending=0 dmacr: 0x00000006
[ 0.844468] sata-dwc 4bffd1800.sata: DMA not pending tag=0x1f pending=0
[ 0.851052] sata-dwc 4bffd1800.sata: sata_dwc_dma_xfer_complete DMA protocol RX and TX DMA not pending dmacr: 0x00000004
[ 0.861976] sata-dwc 4bffd1800.sata: sata_dwc_isr: DMA not pending intpr=0x80000080 status=0x00000050 pending=0
[ 0.872042] sata-dwc 4bffd1800.sata: sata_dwc_clear_dmacr DMA protocol RX and TX DMA not pending tag=0x1f pending=0 dmacr: 0x00000006
[ 0.883988] sata-dwc 4bffd1800.sata: DMA not pending tag=0x1f pending=0
[ 0.890572] sata-dwc 4bffd1800.sata: sata_dwc_dma_xfer_complete DMA protocol RX and TX DMA not pending dmacr: 0x00000004
These are errors.
It looks to me like OpenWrt can't properly deal with (these) SSDs on SATA, or something is wrong/off with them. Someone more knowledgeable than me will have to chime in, I'm out of my depth here.
I've found comments on other forums confirming a bug in the firmware of these SSD drives (e.g. https://bugzilla.kernel.org/show_bug.cgi?id=72341). It is not a showstopper anyway, the device will be used with large HDD's (I've grabbed the first SATA drives for the tests). I will test it further with HDD's.
However, I wonder why does it work properly with one SSD... 
And also, why does it work with the untouched openwrt partitions...
Maybe @chunkeey knows the answer (?).
The MBL has a somewhat troubled relationship with SSDs. I have a 4 GB SSD here the MBL doesn't even attempt to boot off ("doesn't support LBA48", probably a uboot thing). I never tried with "proper" SSDs though, I never considered the MBLs for anything else but the 3.5" disk enclosures they are.
Other than that, I'm sure the SATA driver in OpenWrt could do with some optimization or updating (other members of the forum are pointing out the lack of NCQ), but ... I'm not a developer.
Bad news: it doesn't work with real HDD's neither.
Advice, please!
U-Boot 2009.08-svn54115 (Nov 15 2011 - 10:54:56), Build: 0.0.12
CPU: AMCC PowerPC 4APM82181 Rev. E at 800 MHz (PLB=200, OPB=100, EBC=100 MHz)
Security support
Bootstrap Option E - Boot ROM Location NOR/SRAM (8 bits)
32 kB I-Cache 32 kB D-Cache
Board: Apollo-3G - APM82181 Board, 2*SATA, 1*USB
I2C: ready
DRAM: Auto calibration - \|/-\|/-\ \|/-\|/-\256 MB
FLASH: 512 kB
DTT: 1 FAILED INIT
Net: PHY EC1 Register: 0x2c8c
ppc_4xx_eth0
Type run flash_nfs to mount root filesystem over NFS
e[44me[37mp=============================================================================q
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b=============================================================================de[40m e[37m
Hit any key to stop autoboot: 1 0
USB: OTG-Controller ID(0x4F54) Version(0x290A)
Err detect usb time out hostport.d32 0x00001000
0 USB Device(s) found
scanning bus for storage devices...
0 Storage Device(s) found
** Block device usb 0 not supported
Board is not configured for test. Do normal boot.
----- Checking Boot Partitions -----
SATA DWC initialization 0
init: Waiting for device...
sata_dwc: Device found
scan: Waiting for device...
SATA DWC initialization 1
init: Waiting for device...
sata_dwc: Device found
scan: Waiting for device...
Loading file "/boot/boot.scr" from sata device 1:1 (hdb1)
624 bytes read
1:1
## Executing script at 00100000
SATA DWC initialization 0
init: Waiting for device...
sata_dwc: Device found
scan: Waiting for device...
SATA DWC initialization 1
init: Waiting for device...
sata_dwc: Device found
scan: Waiting for device...
Loading file "/boot/uImage" from sata device 1:1 (hdb1)
2738039 bytes read
Loading file "/boot/apollo3g.dtb" from sata device 1:1 (hdb1)
16384 bytes read
Loaded part 1
## Booting kernel from Legacy Image at 01000000 ...
Image Name: POWERPC OpenWrt Linux-4.14.50
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 2737975 Bytes = 2.6 MB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
## Flattened Device Tree blob at 01800000
Booting using the fdt blob at 0x1800000
Uncompressing Kernel Image ... OK
Loading Device Tree to 00ff9000, end 00ffffff ... OK
[ 0.000000] bootconsole [udbg0] enabled
[ 0.000000] Linux version 4.14.50 (buildbot@builds-03.infra.lede-project.org) (gcc version 7.3.0 (OpenWrt GCC 7.3.0 r6984-fa0275b)) #0 Fri Jun 22 10:22:57 2018
[ 0.000000] Using PowerPC 44x Platform machine description
[ 0.000000] Found legacy serial port 0 for /plb/opb/serial@ef600300
[ 0.000000] mem=4ef600300, taddr=4ef600300, irq=0, clk=7407407, speed=0
[ 0.000000] -----------------------------------------------------
[ 0.000000] phys_mem_size = 0x10000000
[ 0.000000] dcache_bsize = 0x20
[ 0.000000] icache_bsize = 0x20
[ 0.000000] cpu_features = 0x0000000010100040
[ 0.000000] possible = 0x0000000030100040
[ 0.000000] always = 0x0000000000100000
[ 0.000000] cpu_user_features = 0x8c008000 0x00000000
[ 0.000000] mmu_features = 0x00000008
[ 0.000000] -----------------------------------------------------
[ 0.000000] Top of RAM: 0x10000000, Total RAM: 0x10000000
[ 0.000000] Memory hole size: 0MB
[ 0.000000] Zone ranges:
[ 0.000000] DMA [mem 0x0000000000000000-0x000000000fffffff]
[ 0.000000] Normal empty
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000000000000-0x000000000fffffff]
[ 0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x000000000fffffff]
[ 0.000000] On node 0 totalpages: 65536
[ 0.000000] free_area_init_node: node 0, pgdat c055ba30, node_mem_map cfded000
[ 0.000000] DMA zone: 512 pages used for memmap
[ 0.000000] DMA zone: 0 pages reserved
[ 0.000000] DMA zone: 65536 pages, LIFO batch:15
[ 0.000000] MMU: Allocated 1088 bytes of context maps for 255 contexts
[ 0.000000] pcpu-alloc: s0 r0 d32768 u32768 alloc=1*32768
[ 0.000000] pcpu-alloc: [0] 0
[ 0.000000] Built 1 zonelists, mobility grouping on. Total pages: 65024
[ 0.000000] Kernel command line: root=/dev/sda2 rw rootfstype=ext4 console=ttyS0,115200
[ 0.000000] PID hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.000000] Dentry cache hash table entries: 32768 (order: 5, 131072 bytes)
[ 0.000000] Inode-cache hash table entries: 16384 (order: 4, 65536 bytes)
[ 0.000000] Memory: 253952K/262144K available (4584K kernel code, 208K rwdata, 572K rodata, 188K init, 243K bss, 8192K reserved, 0K cma-reserved)
[ 0.000000] Kernel virtual memory layout:
[ 0.000000] * 0xfffdf000..0xfffff000 : fixmap
[ 0.000000] * 0xfde00000..0xfe000000 : consistent mem
[ 0.000000] * 0xfde00000..0xfde00000 : early ioremap
[ 0.000000] * 0xd1000000..0xfde00000 : vmalloc & ioremap
[ 0.000000] SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[ 0.000000] NR_IRQS: 512, nr_irqs: 512, preallocated irqs: 16
[ 0.000000] UIC0 (32 IRQ sources) at DCR 0xc0
[ 0.000000] UIC1 (32 IRQ sources) at DCR 0xd0
[ 0.000000] UIC2 (32 IRQ sources) at DCR 0xe0
[ 0.000000] UIC3 (32 IRQ sources) at DCR 0xf0
[ 0.000000] time_init: decrementer frequency = 800.000008 MHz
[ 0.000000] time_init: processor frequency = 800.000008 MHz
[ 0.000015] clocksource: timebase: mask: 0xffffffffffffffff max_cycles: 0xb881274fa3, max_idle_ns: 440795210636 ns
[ 0.010284] clocksource: timebase mult[1400000] shift[24] registered
[ 0.016592] clockevent: decrementer mult[ccccccef] shift[32] cpu[0]
[ 0.022858] pid_max: default: 32768 minimum: 301
[ 0.027539] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.034064] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.044080] random: get_random_u32 called from 0xc01feab8 with crng_init=0
[ 0.051159] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 1911260446275000 ns
[ 0.060828] futex hash table entries: 256 (order: -1, 3072 bytes)
[ 0.067670] NET: Registered protocol family 16
[ 0.074264] PPC4XX OCM1: 32768 Bytes (enabled)
[ 0.078624] PPC4XX OCM1: 32768 Bytes (non-cached)
[ 0.083283] PPC4XX OCM1: 0 Bytes (cached)
[ 0.087317] debugfs ppc4xx ocm: failed to create file
[ 0.092450] 256k L2-cache enabled
[ 0.095766] PCIE0: Port disabled via device-tree
[ 0.100938] PCI: Probing PCI hardware
[ 0.113513] SCSI subsystem initialized
[ 0.117679] libata version 3.00 loaded.
[ 0.123064] clocksource: Switched to clocksource timebase
[ 0.129028] NET: Registered protocol family 2
[ 0.133774] TCP established hash table entries: 2048 (order: 1, 8192 bytes)
[ 0.140666] TCP bind hash table entries: 2048 (order: 1, 8192 bytes)
[ 0.146955] TCP: Hash tables configured (established 2048 bind 2048)
[ 0.153327] UDP hash table entries: 256 (order: 0, 4096 bytes)
[ 0.159084] UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
[ 0.165416] NET: Registered protocol family 1
[ 0.169712] PCI: CLS 0 bytes, default 32
[ 0.176335] dw_dmac 4bffd0800.dma: DesignWare DMA Controller, 2 channels
[ 0.187243] Crashlog allocated RAM at address 0x3f00000
[ 0.192921] workingset: timestamp_bits=30 max_order=16 bucket_order=0
[ 0.203307] squashfs: version 4.0 (2009/01/31) Phillip Lougher
[ 0.218081] io scheduler noop registered
[ 0.221917] io scheduler deadline registered (default)
[ 0.227299] GPIO line 472 (enable EMAC PHY) hogged as output/low
[ 0.233224] GPIO line 473 (Enable Reset Button, disable NOR) hogged as output/low
[ 0.240642] GPIO line 474 (Power USB Core) hogged as output/low
[ 0.246516] GPIO line 475 (Power Drive Port 1) hogged as output/low
[ 0.252738] GPIO line 479 (Power Drive Port 0) hogged as output/low
[ 0.259732] Serial: 8250/16550 driver, 16 ports, IRQ sharing enabled
[ 0.267741] console [ttyS0] disabled
\CA[ 0.291333] serial8250.0: ttyS0 at MMIO 0x4ef600300 (irq = 19, base_baud = 462962) is a U6_16550A
[ 0.300113] console [ttyS0] enabled
[ 0.300113] console [ttyS0] enabled
[ 0.307006] bootconsole [udbg0] disabled
[ 0.307006] bootconsole [udbg0] disabled
[ 0.315316] console [ttyS0] disabled
[ 0.318934] console [ttyS0] enabled
[ 0.322890] sata-dwc 4bffd1000.sata: id 0, controller version 1.91
[ 0.332862] scsi host0: sata-dwc
[ 0.336318] ata1: SATA max UDMA/133 irq 33
[ 0.340541] sata-dwc 4bffd1800.sata: id 0, controller version 1.91
[ 0.347658] scsi host1: sata-dwc
[ 0.351077] ata2: SATA max UDMA/133 irq 34
[ 0.355580] of-flash 4fff80000.nor_flash: do_map_probe() failed for type cfi_probe
[ 0.363793] of-flash 4fff80000.nor_flash: do_map_probe() failed
[ 0.370342] libphy: Fixed MDIO Bus: probed
[ 0.374441] PPC 4xx OCP EMAC driver, version 3.54
[ 0.379429] MAL v2 /plb/mcmal, 1 TX channels, 1 RX channels
[ 0.385175] RGMII /plb/opb/emac-rgmii@ef601500 initialized with MDIO support
[ 0.392328] TAH /plb/opb/emac-tah@ef601350 initialized
[ 0.397766] /plb/opb/emac-rgmii@ef601500: input 0 in rgmii mode
[ 0.403780] libphy: emac_mdio: probed
[ 0.519815] eth0: EMAC-0 /plb/opb/ethernet@ef600c00, MAC 00:90:a9:3d:80:c1
[ 0.526694] eth0: found Broadcom BCM50610 PHY (0x01)
[ 0.531725] i2c /dev entries driver
[ 0.535320] booke_wdt: powerpc book-e watchdog driver loaded
[ 0.541403] device-mapper: ioctl: 4.37.0-ioctl (2017-09-20) initialised: dm-devel@redhat.com
[ 0.552976] NET: Registered protocol family 10
[ 0.558928] Segment Routing with IPv6
[ 0.562680] NET: Registered protocol family 17
[ 0.567151] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this.
[ 0.580063] 8021q: 802.1Q VLAN Support v1.8
[ 0.685889] ata1: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
[ 0.711269] ata1.00: ATA-8: ST1000LM024 HN-M101MBB, 2AR10002, max UDMA/133
[ 0.718134] ata1.00: 1953525168 sectors, multi 0: LBA48 NCQ (depth 1/32)
[ 0.724903] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
[ 0.733567] ata2.00: ATA-8: Hitachi HTS545050B9A300, PB4OC64G, max UDMA/133
[ 0.740516] ata2.00: 976773168 sectors, multi 0: LBA48 NCQ (depth 1/32)
[ 0.750255] ata1.00: configured for UDMA/133
[ 0.754940] scsi 0:0:0:0: Direct-Access ATA ST1000LM024 HN-M 0002 PQ: 0 ANSI: 5
[ 0.763664] ata2.00: configured for UDMA/133
[ 0.768468] scsi 1:0:0:0: Direct-Access ATA Hitachi HTS54505 C64G PQ: 0 ANSI: 5
[ 0.776718] sd 0:0:0:0: [sda] 1953525168 512-byte logical blocks: (1.00 TB/932 GiB)
[ 0.784361] sd 0:0:0:0: [sda] 4096-byte physical blocks
[ 0.790802] sd 1:0:0:0: [sdb] 976773168 512-byte logical blocks: (500 GB/466 GiB)
[ 0.798611] sd 0:0:0:0: [sda] Write Protect is off
[ 0.803408] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
[ 0.808507] sd 1:0:0:0: [sdb] Write Protect is off
[ 0.813294] sd 1:0:0:0: [sdb] Mode Sense: 00 3a 00 00
[ 0.818453] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[ 0.827524] sd 1:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[ 1.164131] sdb: sdb1 sdb2 sdb3 sdb4
[ 1.168914] sd 1:0:0:0: [sdb] Attached SCSI disk
[ 1.218161] sda: sda1 sda2 sda3 sda4
[ 1.222934] sd 0:0:0:0: [sda] Attached SCSI disk
[ 1.227629] md: Waiting for all devices to be available before autodetect
[ 1.234404] md: If you don't use raid, use raid=noautodetect
[ 1.240452] md: Autodetecting RAID arrays.
[ 1.244552] md: autorun ...
[ 1.247335] md: ... autorun DONE.
[ 1.266126] EXT4-fs (sda2): warning: mounting unchecked fs, running e2fsck is recommended
[ 1.297186] EXT4-fs (sda2): mounted filesystem without journal. Opts: (null)
[ 1.304267] VFS: Mounted root (ext4 filesystem) on device 8:2.
[ 1.310890] Freeing unused kernel memory: 188K
[ 1.437356] init: Console is alive
[ 1.440917] init: - watchdog -
[ 1.482490] random: fast init done
[ 1.500551] kmodloader: loading kernel modules from /etc/modules-boot.d/*
[ 1.527811] usbcore: registered new interface driver usbfs
[ 1.533360] usbcore: registered new interface driver hub
[ 1.538727] usbcore: registered new device driver usb
[ 1.554884] usbcore: registered new interface driver usb-storage
[ 1.561560] kmodloader: done loading kernel modules from /etc/modules-boot.d/*
[ 1.571225] init: - preinit -
[ 1.711519] eth0: link is down
[ 1.715042] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 1.736004] random: procd: uninitialized urandom read (4 bytes read)
Press the [f] key and hit [enter] to enter failsafe mode
Press the [1], [2], [3] or [4] key and hit [enter] to select the debug level
[ 3.518295] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[ 4.868253] mount_root: mounting /dev/root
[ 4.891235] EXT4-fs (sda2): re-mounted. Opts: (null)
[ 4.896393] mount_root: loading kmods from internal overlay
[ 4.913749] kmodloader: loading kernel modules from //etc/modules-boot.d/*
[ 4.921491] kmodloader: done loading kernel modules from //etc/modules-boot.d/*
[ 5.183326] random: crng init done
[ 5.814219] block: attempting to load /etc/config/fstab
[ 5.859871] block: extroot: not configured
[ 5.887761] EXT4-fs (sda1): warning: mounting unchecked fs, running e2fsck is recommended
[ 5.912484] EXT4-fs (sda1): mounted filesystem without journal. Opts: (null)
[ 5.927610] urandom-seed: Seeding with /etc/urandom.seed
[ 5.993969] procd: - early -
[ 5.996947] procd: - watchdog -
[ 6.536949] procd: - watchdog -
[ 6.541958] procd: - ubus -
U-Boot 2009.08-svn54115 (Nov 15 2011 - 10:54:56), Build: 0.0.12
CPU: AMCC PowerPC 4APM82181 Rev. E at 800 MHz (PLB=200, OPB=100, EBC=100 MHz)
Security support
Bootstrap Option E - Boot ROM Location NOR/SRAM (8 bits)
32 kB I-Cache 32 kB D-Cache
Board: Apollo-3G - APM82181 Board, 2*SATA, 1*USB
I2C: ready
DRAM: Auto calibration - \|/-\|/-\ \|/-\|/-\256 MB
FLASH: 512 kB
DTT: 1 FAILED INIT
Net: PHY EC1 Register: 0x2c8c
ppc_4xx_eth0
Type run flash_nfs to mount root filesystem over NFS
e[44me[37mp=============================================================================q
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b=============================================================================de[40m e[37m
Hit any key to stop autoboot: 1 0
=>
I have to confirm. I didn't try all combinations, but I quickly ran into the same problem.
I went with two completely "fresh" drives. It still boots after creating an additional partition on /dev/sda. After I created an additional partition on /dev/sdb, the OpenWrt boot process stops like in your bootlog.
I also tried setting new UUIDs on the disks, and reducing /dev/sdb to a single empty partition. No joy. Judging from when boot broke, it looks like as soon as /dev/sdb carries anything but the default two OpenWrt partition the boot process stops.
This is a true showstopper for the Duo as a two-drive device. Reluctantly paging Dr. @chunkeey again.
Well:
So I guess this would need to be debugged by either one of you... Sorry.
From what I can see from the provided log, there's no "smoking gun" that killed the kernel.
This could be the "bark" of the watchdog, so maybe a meaningful message will get generated if the kernel option CONFIG_BOOKE_WDT is disabled.
Another easy test would be to check the old 17.01.0 images (with 4.4).
Then again, I don't have high hopes and the next step would be to set stdout-path in the DTS, enable the earlycon earlyprintk kernel parameters and compile a kernel with all the debugging features enabled (make kernel_menuconfig) and try again to see if any meaningful error message is generated.
Note:
There's also the crashlog.
[ 0.187243] Crashlog allocated RAM at address 0x3f00000
But I have no idea, if it survives the reboot or not.
Don't be, you've already done so much on the target and we really don't have any right to demand anything.
That being said, I don't need my Duo at the moment anyway, and since we both are in Germany, I could send it over to you if you're interested.
(Also, I'm certainly not able to make a meaningful attempt at debugging at this level. And relaying information to someone more knowledgeable, "remote debugging", is not something I would want to do -- on either side.)
@takimata I totally agree with you.
@chunkeey Thank you very much for your excellent work!
I'm really sorry, this debugging process exceeds my abilities, I'm just a dumb user.
I can't compile the kernel or the firmware image. All I can offer is that I can run any code and grab the logs if I get very detailed instructions. And I'm in Hungary, so lending the device would not be easy.
Until then, here is a more detailed log from the uboot process (debug level 4). Maybe it helps...
Successful boot:
[ 6.177347] procd: - watchdog -
[ 6.180542] procd: Set watchdog timeout: 30s
[ 6.184863] procd: Ping
[ 6.187381] procd: Opened watchdog with timeout 3s
[ 6.192317] procd: - ubus -
[ 6.195224] procd: Create service ubus
[ 6.199086] procd: Start instance ubus::instance1
[ 6.204150] procd: Started instance ubus::instance1[586]
[ 6.210242] procd: running /etc/init.d/ubus running
[ 6.220177] procd: glob failed on /etc/init.d/ubus
[ 6.225896] random: ubusd: uninitialized urandom read (4 bytes read)
[ 6.245425] random: ubusd: uninitialized urandom read (4 bytes read)
[ 6.252075] random: ubusd: uninitialized urandom read (4 bytes read)
[ 6.259029] procd: Connected to ubus, id=f3846929
[ 6.263809] procd: Change state 2 -> 3
[ 6.267605] procd: - init -
[ 6.271246] procd: Parsing inittab - ::sysinit:/etc/init.d/rcS S boot
[ 6.277788] procd: Parsing inittab - ::shutdown:/etc/init.d/rcS K shutdown
[ 6.284737] procd: Parsing inittab - ::askconsole:/usr/libexec/login.sh
[ 6.291477] procd: Parsing inittab - ttyS0::askfirst:/usr/libexec/login.sh
... going on until the prompt ...
Failed boot:
[ 6.457204] procd: - watchdog -
[ 6.460571] procd: Set watchdog timeout: 30s
[ 6.465047] procd: Ping
[ 6.467747] procd: Opened watchdog with timeout 3s
[ 6.472986] procd: - ubus -
[ 6.476236] procd: Create service ubus
[ 6.480627] procd: Start instance ubus::instance1
[ 6.486654] procd: Started instance ubus::instance1[598]
... waits about 30 seconds, and then reboot ...
It's weird...
It fails the very same way with snapshot build (no surprise), and with lede 17.01.4 (!).
To me it means that nobody ever used lede/openwrt with the MBL Duo with two disks. 
1 Like
I just remembered something. Before I did the experiments above, I only ever used my MBL Duo in an attempt to write disk images to drives intended for MBL Single enclosures. Actually, I wanted to make it my "copy machine". That didn't work out so well: Every time I wrote a disk image to a disk, it would write it, but immediately after dd finished it would reboot.
At the time I shrugged it off as anecdotal, I stashed the Duo and moved on. But in light of the bug we found, I think it points to a deeper problem with the system. Something is off with the way it handles drives and/or partitions.
Hope this helps.
Taken from always successfully hard & soft-booted MBL single (18.06 RC1).
Please note the comparison between procd & init sequence:
(snip) no previous init or procd
[ 0.978838] init: Console is alive
[ 0.982403] init: - watchdog -
[ 1.015977] random: fast init done
[ 1.026019] kmodloader: loading kernel modules from /etc/modules-boot.d/*
[ 1.037751] kmodloader: done loading kernel modules from /etc/modules-boot.d/*
[ 1.055263] init: - preinit -
[ 1.213611] eth0: link is down
[ 1.217136] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 1.232503] random: procd: uninitialized urandom read (4 bytes read)
[ 2.038440] eth0: link is up, 100 FDX, pause enabled
[ 2.043447] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[ 4.316340] mount_root: mounting /dev/root
[ 4.330766] EXT4-fs (sda2): re-mounted. Opts: (null)
[ 4.335943] mount_root: loading kmods from internal overlay
[ 4.352148] kmodloader: loading kernel modules from //etc/modules-boot.d/*
[ 4.359654] kmodloader: done loading kernel modules from //etc/modules-boot.d/*
[ 4.528469] block: attempting to load /etc/config/fstab
[ 4.541108] block: extroot: not configured
[ 4.594262] EXT4-fs (sda1): mounted filesystem without journal. Opts: (null)
[ 4.603104] urandom-seed: Seeding with /etc/urandom.seed
[ 4.639416] procd: - early -
[ 4.642430] procd: - watchdog -
[ 4.795345] EXT4-fs (sda3): mounting ext3 file system using the ext4 subsystem
[ 4.802804] random: crng init done
[ 4.924894] EXT4-fs (sda3): mounted filesystem with ordered data mode. Opts:
[ 4.958587] Adding 32764k swap on /root/32M.swap. Priority:-2 extents:1 across:32764k
[ 5.178933] procd: - watchdog -
[ 5.182276] procd: - ubus -
[ 5.236172] procd: - init -
4 more seconds to prompt, with no more init or procd
Edited for typo corrections and more "init/procd" details.
May not be a relevant note:
- /root/32M.swap is user made (a must for transmission-daemon).
- rng-tools installed and /etc/config/system linked to /dev/hwrng (accelerates encrypted torrent stream).
After dd finished it would reboot?
Well, the "sudden" reboots are a thing a watchdog would do. I guess there's an easy way to test this a bit (over serial console).
During boot, the OpenWrt image gives the user the change to enter failsafe:
Pressing "f" here and then entering the failsafe console could help to shed some light into the darkness.
The first thing to check: does the failsafe console come up or does it get stuck (or reboots)?
second: Is it possible to read data from the main disk (sda) and from the second disk?
(i.e. something easy like dd if=/dev/sda of=/dev/null bs=1M count=1 - or hdparm -t /dev/sda if it was installed)
third: what about sda1, sdb1, ...
fourth: try to read-only mount data partition on main and secondary disk.
fifth: read-write remount. (mount -o remount,rw /dev/sda1 ...)
...
@jkthas Thank you, it's more or less the same as MBL Duo with one disk only.
@chunkeey
Failsafe mode is working properly. All the partitions are there, can be mounted (ro and rw), can be read, and can be written (both on partition and filesystem level), without any errors or reboots. The partition table can be updated as well (I used failsafe mode to delete the partitions causing the error).
I tend to think the problem is not directly related to disk access. According to the logs the ubus / urandom process fails (cannot start actually), though I don't have a clue how is it connected to disks or partitions.
No real idea either. I think procd/init gets stuck waiting for something to happen (i.e. blocked io) between:
and
ret = service_update(s, tb, add);
I think it must be somewhere in service_update() just before the call to rc() in
Because otherwise we would see this message to appear on the MBL DUO:
[ 6.210242] procd: running /etc/init.d/ubus running
As for the urandom messages:
[ 6.225896] random: ubusd: uninitialized urandom read (4 bytes read)
These are generated by the kernel's random.c:
And I think the reason why they show up in the bootlog is because ubusd uses /dev/urandom for random id generation in ubus_alloc_id().
I don't think the problem is in ubusd, since otherwise we would simply see a timeout after 50 seconds. Something must be blocking in procd and because of this the procd daemon does no longer ping the watchdog.... And hence the MBL DUO reboots.
One more strange thing (two disks, untouched openwrt):
[ 8.780355] eth0: link is up, 1000 FDX, pause enabled
[ 8.785520] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 8.791385] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[ 1024.543024] random: crng init done
It seems that the random process is not initialized properly in the boot process. This message always comes a few minutes later. I haven't seen such a thing on any other device.
edit:
There is delay on other platforms as well (x86 virtual machine with 18.06-rc1), but much less:
[ 5.533512] kmodloader: done loading kernel modules from /etc/modules.d/*
[ 15.060086] random: crng init done
[ 15.070062] random: 1 urandom warning(s) missed due to ratelimiting