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brent
Asked: 2010-10-23 09:29:21 +0800 CST

Poor performance from SAS disks on HS22 blade in CentOS/RHEL on ESXi 4.0

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I have an HS22 blade configured with two 600GB 10K 6Gbps SAS drives configured in RAID1 using the onboard LSI Logic controller. Running on it is VMWare ESXi 4.0u2, and on top of that are a couple VMs. (Yes, I'm aware that we should be providing storage via SAN, but this was a budgetary constraint) I'm seeing poor read/write performance

  • Host A: RHEL 5.5, 8GB RAM, 2 vCPUs
  • Host B: CentOS 5.5, 1GB RAM, 2 vCPUs

Both kernels are configured to boot with elevator=noop

Result of ~8GB dd on Host A to a 350GB thin-provisioned disk, ext3 formatted:

# dd if=/dev/zero of=fullram bs=1K count=8388608
8388608+0 records in
8388608+0 records out
8589934592 bytes (8.6 GB) copied, 467.934 seconds, 18.4 MB/s

The maximum write performance I've seen is ~30MB/s (monitored through vSphere client)

Result of ~8GB dd on Host B to a 40GB thin-provisioned disk, ext3 formatted:

# dd if=/dev/zero of=fullram bs=1K count=8388608      
8388608+0 records in
8388608+0 records out
8589934592 bytes (8.6 GB) copied, 478.192 seconds, 18.0 MB/s

The maximum write performance I've seen for this VM however is about 50MB/s (monitored through vSphere client)

I've tested read performance on Host A in the following way:

  1. dd a 1GB file
  2. dd a second file to the same size as RAM (8GB)
  3. Read the 1GB file with dd

Result was:

# dd if=testfile of=/dev/null bs=1K
2097152+0 records in
2097152+0 records out
2147483648 bytes (2.1 GB) copied, 190.255 seconds, 11.3 MB/s

I'm at a loss for what could be causing this issue

performance hard-drive linux vmware-esxi bladecenter

2 Answers

  1. Thin is slower, have you tried thick for comparison?

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  2. Best Answer

    Seriously - what do you expect? 19k SAS drives are not exactly stelar in perforamnce and you put up a LOT of stuff onto one blade. Get a storage blade or a SAN behind it.

    To give you a comparison - I run a dual Opteron Hyper-V server with 64gb RAM.... Using Velociraptors 10k RPM drives 300gb earch (roughly -comparable to your discs - lets sqay a little slower).

    But I use 6, soon 8 of those to get the IOPS budget I need for that server, and db intensive stuff (a database) uses ANOTHER 86 discs in RAID 10 mode.

    Basically a RAID 1 is physically limited. You will need to put in a lot more discs, and blades are NOT well suited for that, unless your blade can get what IBM calls storage blades (basically a blade with just discs, no processor, but quite some of them).

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