> i have a system where raidframe accesses are severely restricted > and present a 2-20x performance loss.
to followup on this: the problem has disappeared from normal raidframe accesses even with the same kernels that were previously not working great. i've since had the disk i was using both the underlying filesystem, or when the mirror was in single sided mode fail [*], and i have been able to confirm that the "slow parity rebuild" problem appears to also be helped by a higher HZ setting. with HZ=100 resyncing to the replacement disk tops out at 6.4MB/sec (100*64KB). with HZ=1024 it is more like 62MB/sec (just under 1000*64KB). i haven't actually instrumented this to confirmm it but it seems likely. [*] since the accesses to this disk were always fast from the underlying disk except for a special case mlelstv has concocted, and that the general slowness disappeared before the disk failed, i am confident that the failure isn't related. .mrg.
