XFS: Abysmal write performance because of excessive seeking (allocation groups to blame?)

[Peter Grandi]

[ ... ]

> For metadata intensive workloads like yours you would be much
> better using a non-striping raid, e.g. concatentation and
> mirroring instead of raid 5 or raid 6. I know this has a cost
> in terms of "wasted" space, but for IOPs bound workload the
> difference is dramatic.

The problem with parity RAIDs and small-write-IO intensive
workloads is not striping as such, it is with *large* stripes.
That is a detail that matters quite a lot.