Re: Horrible drive performance under concurrent i/o jobs (dlh problem?)

[Con Kolivas]

>So copied everything away to a software raid and tried all the disk 
>tuning stuff (min-, max-readahead, bdflush, elvtune). Nothing helped. 
>Last Sunday I then found a hint about a bug introduced in kernel 
>2.4.19-pre6 which could be fixed using a "dlh", disk latency hack - or 
>going back to 2.4.18. Last is what I did ( from 2.4.20 )

I made the dlh (disk latency hack) and it is related to a problem of system
response under heavy IO load, NOT the actual IO throughput so this sounds
unrelated. However, I have seen what you describe with reiserFS and ide raid at
least and had it fixed by applying AA's stuck in D fix, which ReiserFS is more
prone to for some complicated reason. Give that a go.

In 

http://www.kernel.org/pub/linux/kernel/people/andrea/kernels/v2.4/2.4.20aa1/

it is patch 9980_fix-pausing-2         

Regards,
Con