bug#51787: Disk performance on ci.guix.gnu.org

[Mathieu Othacehe]

Hey,

> This is still pretty bad, but better than the <1M performance suggested
> by previous runs.

Mmh interesting, I also have a x10 speed up on sdb by increasing the
block size from 4k to 512k. I'm not sure what conclusion should we draw
from this observation.

In particular for our most urging matter, /gnu/store/trash
removal. Moving to a faster hard drive would definitely help here, but I
still don't understand if that disk performance regression comes from
Linux, the file-system fragmentation, or the disk itself.

>    READ: bw=1547MiB/s (1622MB/s), 1547MiB/s-1547MiB/s (1622MB/s-1622MB/s), 
> io=3055MiB (3203MB), run=1975-1975msec
>   WRITE: bw=527MiB/s (553MB/s), 527MiB/s-527MiB/s (553MB/s-553MB/s), 
> io=1042MiB (1092MB), run=1975-1975msec

Wooh that's fast! On test could be to copy the /gnu/store/trash content
to the SAN an observe how long that it takes for this operating to
complete.

Thanks for your support on that complex topic :)

Mathieu