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OpenFiler iSCSI RAID 5 Card

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1:15 pm
27 January, 2010

chriskyte

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Hi Everyone,

I am looking for a battery backed PCIe based RAID card to install in an ML115 G5 Server to run OpenFiler and provide iSCSI storage to 3 ESXi hosts. I have been looking at the HP E200 or Dell Perc 5/i and am torn between which one would give me best performance.

I have 6 X 500GB WDRE3 Drives and am planning on running a RAID 5 (4 disk) and a RAID 1 (2 disk) configuration.

Can anyone offer any guidance as to which card would be best or suggest an alternative card. My budget is £300.

Thanks

Chris

12:58 pm
3 February, 2010

James Pearce

Moderator

posts 28

2

Hi

The Perc 5 has a faster processor than the E200, but I think the proposed disk config might be more of an issue. With a four-drive Raid-5 array, the random write performance is that of one disk, whilst the random read should be about 3x that. However running it as a 6-drive Raid-10 array, (which would have the same capacity as a four-drive Raid-5 array) the random read performance will be near to 6x that of a single drive and random write roughly 3x.

Typically storage is something like 70% read – on that basis the 6-drive Raid-10 array should perform well over twice as well as the 4-drive Raid-5 with random workloads.

To illustrate this in practice, I recently benchmarked a Perc-5 with 3x 500GB RE2's Raid-5 against a 4x 500GB RE2 Raid-10 array. With 8K random workload, 70% read, the Raid-5 turned in about 220 IOPS. The same workload n the Raid-10 array touches 500 IOPS and has considerably lower latency (32ms at 16 outstanding IOs, vs 73ms).

If you choose to go this route the processing speed of the card is far less important and either option should provide about the same throughput. As you say, having the BBWC is important though.

Hope that helps.

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