Ive been trying to overcome performance problems with software raid0,
currently under 2.[34] a single drive has better read performance than a
4-way ide raid0 (striping), write performance seems to be limited to
about 30MB/s, for me ide raid just doesnt scale well at all. Ive
mentioned this on linux-raid mailing list and Ingo says that scsi scales
well acording to his tests. Others on the list also noted poor ide
performance.
So... i think ide could have some performance limitations that are only
noticable when using multiple disks.
I modified hdparm to use 1280MB for Timing buffer-cache-reads to do the
benchmark.
I do hdparm -T /dev/hde i get 86MB/s then i do hdparm -T /dev/hdi i get
86MB/s
If i do them both at the same time i get 43MB/s for each.
The drives are udma66 each on there own promise udma66 pci card,
detected and used by the kernel as udma66.
Shouldnt the performance of these drives be independent of each other,
why would one drive slow the other down ?
I run it on a dual 433 celeron with 128MB ram, when i run only one
instance of hdparm it uses 50% of cpu resources, when i run both
concurrently combined they use 100% (aprox). So i assume hdparm isnt
multi-thrreaded, given this i dont think cpu resource should be causing
the bottleneck.
Could this be a software (kernel) limitation rather than hardware ?
Thanks
Glenn
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