[H-GEN] Disk transfer speeds

[Michael Anthon]

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I'm not quite "up" with this stuff yet.  I'm just in the process of 
installing Debian on to my bright and shiny new Proliant DL380 at work 
and I'm curious about the disk speeds.

I have 2 disk systems set up.  The first is using the internal 5i array 
controller and is 3 disk in RAID0+1 with a hot spare.  The second is 
using a 5312 array controller with 5 disks in a RAID5 setup.  I did some 
very rough benchmarks just to see what sort of raw speed these would give.

dd if=dev/zero of=test bs=1M count=1024
1073741824 bytes transferred in 17.238604 seconds (62287052 bytes/sec)
dd if=test of=/dev/null
1073741824 bytes transferred in 14.535972 seconds (73867906 bytes/sec)

dd if=dev/zero of=test bs=1M count=1024
1073741824 bytes transferred in 14.047853 seconds (76434586 bytes/sec)
dd if=test of=/dev/null
1073741824 bytes transferred in 14.170155 seconds (75774882 bytes/sec)

The first test is the internal array, the second is the external.  Given 
that both controllers are U320 I would have thought the second one would 
give a better result.  I guess the question I really need to ask is what 
sort of performance should I expect to see from this setup ?  AS far as 
I can tell, the RAID 0+1 is reading at most 2 disk simultaneously which 
would give about 36MB/s sustained reading rate per disk.  The RAID5 
setup should be reading 5 disks simultaneously, one of which is parity 
data and "wasted".  I would have thought in this case that I should get 
a much higher sustained rate.

Maybe I'm missing the point somewhere ?

Cheers
Michael


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