[mythtv-users] Software RAID and ionice

[John Drescher]

> That is what I mean by RAID5 having horrible small write performance.
> While all other performance numbers are similar (except for RAID5
> seq-create which is much faster, not sure why it is 10x faster than
> the single disk, and RAID5 random reads which is ~3x faster as
> expected), small write performance such really, really sucks.
>
Small random write performance sucks because the entire raid block
will read from the disk  (unless it is in cache) then the parity is
generated and then the entire raid block is flushed back to cache and
eventually it is written to disk.

John