Hello Richard ,
On Wed, 16 Jul 2008, Richard Scobie wrote:
Michal Soltys wrote:
Also looking back at other benchmarks, stripe_cache_size can have pretty
tremendous effect on md raid performance. There're other settings that
could matter as well (read ahead, queue depths). It would be interesting to
see e.g. raid5 256k chunk comparison, done with those altered (
_especially_ md's stripe_cache_size with some high value like 16384 or
32768), and with stripe-width used in ext3 case (if it wasn't used
already).
Agreed. On a 16 SATA drive SAS attached md RAID6, large streaming write
performance goes from around 110MB/s with the default stripe_cache_size, to
600MB/s using 16384.
There are major read performance too, setting readahead on the md device to
65536.
At what level (2.6.26) does one set readahead ?
I've searched 'mount' , 'mdadm' , 'Documentation/md.txt' . Where
else should I look ? Obviously I am missing something .
Regards,
Richard
TIa , JimL
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