Re: which dual-CPU hardware/OS is fastest for PostgreSQL? - Mailing list pgsql-performance

From Jan Dittmer
Subject Re: which dual-CPU hardware/OS is fastest for PostgreSQL?
Date
Msg-id 41E856A7.6080804@portrix.net
Whole thread Raw
In response to Re: which dual-CPU hardware/OS is fastest for PostgreSQL?  (Greg Stark <gsstark@mit.edu>)
List pgsql-performance
Greg Stark wrote:
> Jan Dittmer <j.dittmer@portrix.net> writes:
>
>
>>You could always do raid 1 over raid 0, with newer kernels (2.6ish)
>>there is even a dedicated raid10 driver.
>
>
> Aren't you much better off doing raid 0 over raid 1?
>
> With raid 1 over raid 0 you're mirroring two stripe sets. That means if any
> drive from the first stripe set goes you lose the whole side of the mirror. If
> any drive of the second stripe set goes you lost your array. Even if they're
> not the same position in the array.
>
> If you do raid 0 over raid 1 then you're striping a series of mirrored drives.
> So if any drive fails you only lose that drive from the stripe set. If another
> drive fails then you're ok as long as it isn't the specific drive that was
> paired with the first failed drive.


Ever heart of Murphy? :-) But of course you're right - I tend to mix up
the raid levels...

Jan

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