gvinum raid5 performance seems slow
R. B. Riddick
arne_woerner at yahoo.com
Mon Oct 30 07:05:34 UTC 2006
--- Greg 'groggy' Lehey <grog at FreeBSD.org> wrote:
> "Sufficiently large data blocks" equates to several megabytes.
> Currently MAXPHYS, the largest transfer request that would get to the
> bio layer, is 131072 bytes. This would imply a stripe size of not
> more than 32 kB for a five disk array, which is unrealistically small.
> I did consider this optimization, but it would only work if Vinum were
> first to buffer multiple requests, and there are all sorts of
> reliability issues there. For example, you'd have to lie about the
> first few requests that were only buffered and not actually sent out
> to disk. Possibly it should be done anyway.
I did it that way in my graid5 class:
The source might look somehow incomprehensible, but it seems to be quite stable
(on amd64 and i386)...
I tried to benchmark with a 3 disk array:
Single disk: 30MB/sec write speed
graid5 device: 20MB/sec write speed
I would be interested in other benchmarks about it.
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