OpenWRT One NAND Flash Layout

Installing and Using OpenWrt
1

I'm currently using a Linksys EA7300 v2, but I've already run against the limit of its flash (24 MB). So I'm considering replacing it with a device that either offers a larger overlay filesystem in onboard flash or some box that can use e.g. an SD card as system device. I already own a NanoPi R4S that could serve, but I'd rather have a box with more Ethernet ports, maybe even 2.5 Gbps.

So the One is a candidate. Alas, I can't find detailed technical data, especially the NAND flash layout. Does anybody at least have the size of the overlay filesystem? And I'd like to know if the One can boot from NVMe.

2

You can find schematics and datasheets Here

3

Thanks, but I had already found that. It does not contain the information I require, namely the NAND flash layout and implicitly or better explicitly, the size of the Overlay filesystem. Or more details on the boot process.

That may be buried in the sources, but I haven't worked with the OpenWRT source except that a long time ago I built my own snapshot because at the time support for my new router was not in the snapshots provided by the OpenWRT builds. And I don't have the time or patience to delve into the sources now.

I was hoping somebody who already has a One could check that for me. It is not really covered in the c't article. Except for

Das Betriebssystem kommt von einem 256 MByte fassenden NAND-Flash-Chip, was reichlich Platz für funktionale Erweiterungen mit Add-ons lässt.

Ample room is very relative, given the contortions Linksys made the 128 MB NAND go through to arrive at 24 MB for the overlay.

Sigh. I'll just wait until the One is being delivered to everybody, not just reviewers.

4

I had an idea that the flash layout may be listed in at least some of the Banana Pi device pages, and indeed I found two. They hint at an f2fs of a bit over 90 MB, which makes sense.

BananaPi BPI-R3
BananaPi BPi-R64 V1.1, V1.2

So the One may be in the same range or above, given that it has 256 MB NAND. Both devices above have only 128MB. The flash layout for the R64 lists 7.3G free on mmcblk0, but that is an SD card. I assume the layout in the used portion of the card reflects that the onboard NAND flash would use.

Still not good enough to order a One, but looking brighter.

Especially now that I found a paragraph in the c't review I had overlooked:

The mass storage can be easily expanded thanks to the M.2 slot (2230, 2242). It offers a PCIe 2.0 lane, i.e. up to 500 MByte per second gross transfer rate. The developers have announced that the slot will be bootable with a future U-Boot update, so that Linux distributions such as Debian, which do not fit on the NAND flash, can also be started.

(Translated with DeepL)

Still holding for confirmation on the flash layout.

5

Does this help.

 -----------------------------------------------------
 Openwrt One - Build 003 r28131+5-dea839773c, 11-19-2024 SNAPSHOT
 -----------------------------------------------------
root@RuralRoots:~# df
Filesystem           1K-blocks      Used Available Use% Mounted on
tmpfs                   504728     37844    466884   7% /tmp
overlayfs:/overlay      184644      3172    176632   2% /
tmpfs                      512         0       512   0% /dev
/dev/nvme0n1p1        65478188      2060  62104304   0% /mnt/ssd
/dev/nvme0n1p2         4046560    102564   3717900   3% /mnt/usb
/dev/nvme0n1p3         4046560      8736   3811728   0% /mnt/shared
/dev/nvme0n1p5         4046560    197252   3623212   5% /mnt/data
/dev/nvme0n1p6         4046560      2760   3817704   0% /mnt/testing
/dev/nvme0n1p7        40187496      2056  38111824   0% /mnt/scratch
/dev/ubi0_5             184644      3172    176632   2% /mnt/ubi0_5
6

YES! Thanks a lot!

That's what I wanted. So the overlay filesystem has roughly 175 MB. Quite a bit more than my Linksys and about twice as much as BPi-R3 and R64.