Dissapointing performance of ciss RAID 0+1 ?

Pete French petefrench at ticketswitch.com
Thu Nov 9 01:13:58 UTC 2006

I recently overhauled my RAID array - I now have 4 drives arranged
as RAID 0+1, all being 15K 147gig Fujitsu's, and split across two
buses, which are actively terminated to give U160 speeds (and I have
verified this). The card is a 5304 (128M cache) in a PCI-X slot.

This replaces a set of 6 7200 rpm drives as RAID 5 which were running at
40meg speeds due to non LVD termination. I would expect to see a large speed
increase wouldn't I ? But it remains about the same - around 45 meg/sec
for reading a large file (3 gig or so) and half that for copying said
file. These are 'real world' tests in the sense that I us the drive for
building large ISo images and copying them around - I really dont care what
benchmarks say, it's the speed of these two operatiosn that I want to make

I've tried all the possible stripe sizes (128k gives the best performance)
but still I only get the above speeds. Just one of the 15k drives on it's
own performs better than this! I would expect the RAID-0 to give me at
least some speedup, or in the worst case be the same, surely ?

Booting up Windowws and running some tests gives me far better performance
however, so I am wondering if there is some driver issue here. Has anyone
else seen the same kind of results ? I am running the latest stable for
amd64 and the machine has twin opteron 242's with a gig of RAM each. surely
it can do better than this ?


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