Very low disk performance on 5.x

[Poul-Henning Kamp]

In message <427626DC.5030702 at centtech.com>, Eric Anderson writes:

>Don't mean to be terse here, but I'm talking about the same test done an 
>two different RAID5 configurations, with different disks, and not just 
>me - other users in this very thread see the same issue..

Uhm, if you are using RAID5 and your requests are not aligned and
sized after the RAID5 you should *expect* read performance to be poor.

If you your request ends up accessing two different blocks even just
once per stripe, this totally kills performance.


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