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I have an HP DL380 G5 with a P212 controller and a 256MB cache card/battery.

The P212 is hooked up to an MSA60 enclosure, which for testing, I have populated with 8x 500GB 7.2k SATA disks.

I know after a lot of research, that the MSA60 will only negotiate SATA disks at 1.5G, and that the single SAS cable between the controller and enclosure has 4x 300MB/s lanes.

So the max speed over the link is 1,200MB/s, and if I know how RAID0 works correctly, I should get very fast read/write speeds on a RAID0 of 8 disks.

I did a simple crystal disk mark test, and saw it cap at around 360MB/s read. Is that what I should be expecting on this setup, as I thought it would be higher than that.

Maybe my maths skills aren't up to scratch.

EDIT

So thanks to everyone's input which confirms my understanding of SAS links, the link between the enclosure and controller is not the bottleneck.

What I have started using now, is 4 x 3TB Seagate 7200RPM drives. What is odd, is that two of them are showing with link speeds of 1.5Gbps, and 2 show as 3Gbps.

A disk test on a single disk shows that reads are around 140MB/s, and writes around 110MB/s. If I scale up in RAID0, each disk I add scales the write speeds as expected, with 4 disks providing around 440MB/s. Reads however, seem to reach a maximum of about 410MB/s, but I would expect around 560MB/s in RAID0.

Could this scaling be down to cache settings perhaps?

I would like to use RAID 5 in this enclosure, but if I can't get expect results with RAID 0, I dread to think what my RAID 5 results will be.

  • You do realize that SAS/SATA speeds are noted in gigabits, while your benchmarks are probably returning you numbers in gigabytes. There's a slight difference, and 360MB/s probably means you're getting almost 3Gbits/s out of your enclosure. – GregL Feb 10 '16 at 12:44
  • Yes, I realise they are noted differently. My confusion is most likely around the maximum bandwidth between the enclosure and controller. It is a 4 lane connection, so does that mean it has 4x 3Gbps lanes, or a total max link of 3Gbps? If the total link speed between the two is 3Gbps, that would be my bottleneck of 360MB/s – James Edmonds Feb 12 '16 at 19:06
  • I won't try and answer those questions, because thankfully, SF already has some highly relevant answers. It seems @ewwhite is sort of a guru around here. – GregL Feb 12 '16 at 19:13
  • Yes he does seem to be the man in the know. All that confirm my understand of SAS bandwidth and lanes, so can safely say my bottleneck doesn't lie in the link between enclosure and controller. – James Edmonds Feb 13 '16 at 17:02
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I measured similar performance on a DL360G6, HBA SAS 9212-4i4e controller (JBOD) and 12x 3TB ZFS system. I never saw throughput higher than 400 MB/sec.

Keep in mind that the MSA60 is quite old (10y+)

  • Thanks for this. So I suspect this confirms that I was wrong about how the link between the enclosure and controller works, in that the total bandwidth between the two over 1 SAS cable is 3Gbps, which works out at 375MB/s? – James Edmonds Feb 12 '16 at 19:07

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