[OpenIndiana-discuss] Recommendations for fast storage

[Timothy Coalson]

On Tue, Apr 16, 2013 at 4:29 PM, Sašo Kiselkov <skiselkov.ml at gmail.com>wrote:

> If you are IOPS constrained, then yes, raid-zn will be slower, simply
> because any read needs to hit all data drives in the stripe. This is
> even worse on writes if the raidz has bad geometry (number of data
> drives isn't a power of 2).
>

Off topic slightly, but I have always wondered at this - what exactly
causes non-power of 2 plus number of parities geometries to be slower, and
by how much?  I tested for this effect with some consumer drives, comparing
8+2 and 10+2, and didn't see much of a penalty (though the only random test
I did was read, our workload is highly sequential so it wasn't important).

Tim