Edit: I did some more tests and I have to extensively edit my numbers regarding the original MBL.
Edit 2: I repeated the tests on OpenWrt with a fully initialized ext4 file system (disabled ext4 lazy init), getting slightly better results at writing and much better results at reading.
This is my testing process:
root@OpenWrt:~# hdparm -tT /dev/sda
/dev/sda:
Timing cached reads: 452 MB in 2.00 seconds = 225.80 MB/sec
Timing buffered disk reads: 242 MB in 3.00 seconds = 80.65 MB/sec
root@OpenWrt:~# hdparm -tT --direct /dev/sda
/dev/sda:
Timing O_DIRECT cached reads: 178 MB in 2.02 seconds = 88.26 MB/sec
Timing O_DIRECT disk reads: 258 MB in 3.01 seconds = 85.69 MB/sec
root@OpenWrt:/mnt/sda3# time dd if=/dev/zero of=tempfile bs=1M count=1024
1024+0 records in
1024+0 records out
real 0m 37.94s
user 0m 0.01s
sys 0m 10.82s
root@OpenWrt:/mnt/sda3# time dd if=tempfile of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
real 0m 12.36s
user 0m 0.01s
sys 0m 5.94s
root@OpenWrt:/mnt/sda3# hdparm -W0 /dev/sda
/dev/sda:
setting drive write-caching to 0 (off)
write-caching = 0 (off)
root@OpenWrt:/mnt/sda3# time dd if=/dev/zero of=tempfile bs=1M count=1024
1024+0 records in
1024+0 records out
real 0m 48.12s
user 0m 0.01s
sys 0m 10.51s
root@OpenWrt:/mnt/sda3# time dd if=tempfile of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
real 0m 12.36s
user 0m 0.01s
sys 0m 5.90s
It works out like this:
OpenWrt on 4 TB WD Red (WD40EFRX):
- hdparm direct disk read: 86 MB/s
- dd write on ext4, write-caching on: 27 MB/s
- dd write on ext4, write-caching off: 21 MB/s
- dd read on ext4: 82 MB/s
Original MBL 1TB (presumably WD Green):
- hdparm direct disk read: 121 MB/s
- dd write on ext3, write-caching on: 94 MB/s
- dd write on ext3, write-caching off: 5 MB/s
- dd read on ext3: 98.9 MB/s
Original MBL 2TB (presumably WD Green):
- hdparm direct disk read: 117 MB/s
- dd write on ext3, write-caching on: 40 MB/s
- dd write on ext3, write-caching off: 5 MB/s
- dd read on ext3: 42 MB/s
My 1 TB MBL shows the performance I'm used to, but my 2 TB MBL is clearly not performing very well, I assume that's because it has been in use for a long time and is rather full. I will have to look into that, but that drive is scheduled for OpenWrt conversion anyway. Of note is that the original MBL's write performance consistently and significantly breaks down when write-caching is disabled. At any rate, take the comparison values to the original MBL with a grain of salt, the drives are of course of varying degrees of use and vintage.
In comparison, writing to disk under OpenWrt is quite a bit slower, which I assume is owed to the smaller block size. Reading speeds seem to be much less affected by block sizes and turn out to be roughly in the same ballpark as with the original MBL.
