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