Very Poor Disk Performance SAS 15000 RPM Drives

JustinK101 · 07-02-2008, 07:01 PM

Running A Virtual Linux Server Fedora 9 Under Host Windows 2003 Server x64 with VmWARE Server.

The physical machine has 2 drives in RAID 1, and the drives are SAS 15,000 RPM drives.

On the Linux box, when I run the benchmark:

$ hdparm -tT /dev/sda

Timing cached reads: 4569.14 MB/Sec
Timing buffered disk reads: 8.50 MB/Sec

Doesn't this seem VERY slow for disk reads? Are there any linux hard drive benchmarks I can try in addition? Any settings I should be looking at?

amani · 07-02-2008, 07:23 PM

Strange hard drive... only the cache seems to be working !

You can use bonnie+

JustinK101 · 07-02-2008, 08:02 PM

Any other ideas? Any commands to try to see config?

Mr. C. · 07-02-2008, 08:14 PM

You're running a virtualized system. hdparm will be affected greatly by the underlying host. Read the descriptions for -t and -T. Run on an otherwise quiet system, with plenty of free RAM. I don't think a virtualized system can be condsider "quite".

Run a benchmark as amani suggested to test your disk performance, but understand you are testing many more layers that just the disk performance in such a setup.

syg00 · 07-02-2008, 08:57 PM

With all the "rah-rah" about virtualization and vt support and all, everyone forgot about the I/O.
Your virtual guest is just disk file - probably compressed, and probably copy on write. And the VMWare server is just a process as far the operating system is concerned. So, even if the VMWare is doing direct I/O, there's a fair bit of gumph in the way. Running (I/O) performance tests from the guest is unlikely to be overly beneficial. No harm in trying.