I realise this is not a knoppix problem, just hoping for frendly pointers and direction.

I have updated to knoppix 6.4.4 with kernel 2.6.37 and I have discovered a big problem for me with testing scsi hard drives using the sg(x) driver, compared to Knoppix 6.0 with a 2.6.28.4 kernel.
Just one of the many ways I have found to use knoppix, is as a scsi hard drive test environment. I have been using knoppix with kernel 2.6.28.4 for a number of years very sucessfuly.

I commonly test 14 scsi drives simultaneously in an external drive bay using for example scsi write-same "erase" command. Although we use a product from santools, smartmon-ux, sg_write_same is available form scsitools etc. The performance from this new kernel makes the test operation impractical.

Although, I can test one drive at a time under 2.6.37 with the same test time as 2.6.28.4, as soon as I load additional drives the test times sore from 18m to 134m. To make clear this does not happen under 2.6.28.4, and the write-same command takes very little I/O overhead.

I have tried googling and come across I/O throttling. Am I on the right lines?
I have attempted to research cgroups but the info is mainly on limiting throughput.
I have posted on the linux kernel mailing list, those guys are very, very busy.
Any ideas would be appreciated, happy to run any tests etc. Many reasons why I would like to keep 2.6.37.

Regards,

Will