On Sat, Dec 05, 2009 at 08:57:55AM +1100, Amos Shapira wrote:
Hello,
When approaching hosting providers for services, the first question many of them asked us was about the amount of IOPS the disk system should support.
While we stress-tested our service, we recorded between 4000 and 6000 "merged io operations per second" as seen in "iostat -x" and collectd (varies between the different components of the system, we have a few such servers).
A couple of hosting providers told us that this (iostat and collectd "merged operations per second") is a not so bad way to get IOPS.
A partner of ours doubts that this is possible with the current hardware - a 3ware 9690SA-4I4E (http://www.3ware.com/products/sas-9690SA.asp) with 512Mb battery backed up cache and 8 SAS 15k rpm disks (SEAGATE ST3300656SS) in RAID 1+0. They calculate 750 IOPS per spindle and say that the maximum they ever saw from any 15k disk was 350 iops on RAID 0.
Am I measuring the numbers correctly? Is there a better way to measure IOPS on CentOS?
The OS is CentOS 5.3 x86_64, the rest of the hardware is 64Gb RAM, 2 quad-core 3GHz Intel Xeon CPU's.
I typically would look at the tps numbers (either in iostat or sar -b). You might also be able to use blktrace output (combined with seekwatcher) to generate IOPS data.
Someone out there may have some better suggestions.
Ray