jorgitogutierre
Contributor
Contributor

Poor performance of RDM vs VMFS

I have two Proliant ML370 servers with VSphere 5.0, both connected to an external HP MSA2212 Fiber channel storagee.

I noticed a very poor performance when using RDM LUNs compared to VMFS. I used DiskSPD to test IOPs, throughput and average latency.

For example: LUN: 600GB - RAID 1

Test A): random reads of 8Kb blocks

Using RDM: 2 MB/sec throughput

Using VMFS: 250 MB/sec throughput

Test B): sequential reads of 512Kb blocks

Using RDM: 5 MB/sec throughput

Using VMFS: 1500 MB/sec throughput

Desperately need some help!

Jorge

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2 Replies
rcporto
Leadership
Leadership

Did you run the test from the same source (VM) ? How is the virtual SCSI device configuration ?

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Richardson Porto
Senior Infrastructure Specialist
LinkedIn: http://linkedin.com/in/richardsonporto
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jorgitogutierre
Contributor
Contributor

Yes. I ran both tests in a new Windows 2008 VM and an existing one. In both machines the tests are the same.

SCSI controller 0: LSI Logic SAS. Bus sharing: None

Mapped RUN LUN: Physical mode.

Thanks for your time!

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