2.6.37 kernel poor sg(x) driver scsi hard drive performence

From: Steve Allen
Date: Mon Mar 21 2011 - 08:25:46 EST


My first post, apologies if asking the wrong question in the wrong place. E=
ndeavoured to be correct, read FAQ & searched mailing lists.

I have a specific use of linux as a scsi hard drive test environment. I hav=
e been using knoppix with kernel for a number of years very sucess=
I test 14 drives simultaneously in an external drive bay using for example =
scsi write-same erase command. Although we use a product from santools, sma=
sg_write_same is available form scsitools etc.

I have updated to knoppix 6.4.4 with kernel 2.6.37 and cannot test in the s=
ame manner, the performance makes the test operation impractical.
Although, I can test one drive at a time under 2.6.37 with the same test t=
ime as, as soon as I load additional drives the test times sore =
from 18m to 134m.

I have tried googling and come across I/O throttling. Am I on the right lin=
I have attempted to research cgroups but the info is mainly on limiting thr=

Any ideas would be appreciated, happy to run any tests etc.
Many reasons why I would like to keep 2.6.37


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