[CentOS-virt] disk i/o benchmarking inside vm
stoyan at marinov.us
Mon Oct 10 15:08:08 EDT 2011
OK, I think I managed to fix it. Please check and let me know.
On Oct 10, 2011, at 9:43 PM, Dennis Jacobfeuerborn wrote:
> On 10/10/2011 08:27 PM, Nehemiah wrote:
>> but thats what I'm asking you to investigate. All you see is a symptom,
>> more data may clarify the situation. Weren't you taking data from both
>> inside the guests an on the host's disks. It was kind of unclear.
> The guest number are the ones that are not consistent with each other or
> across restarts of the guests:
> guest 1: 120 seeks/s
> guest 2: 220 seeks/s
> "hdparm -t" shows:
> guest 1: 100 MB/s
> guest 2: 160 MB/s
> The host numbers are the ones of the physical drives:
> /dev/sdb: 75 seeks/s
> /dev/sdc: 75 seeks/s
> hdparm -t:
> /dev/sdb: 140 MB/s
> /dev/sdc: 140 MB/s
> The physical numbers are consistent and what I would expect to see from the
> sata drives.
> The guests are minimal centos 6 installations so after booting they have
> virtually no processes running that could influence the benchmarks in any
> significant way. The hosts system is installed on /dev/sda so /dev/sd(b|c)
> are not influenced by the host system either.
> The entire setup is arranged to make benchmarking mostly reliable.
> If there were minor temporary fluctuations I would blame some external
> process but differences of almost 100% that are consistent for the lifetime
> of the virtual machine do not fit such a scenario.
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