Not getting more than 65000 IOPS with xtreme setup
Hi,
Together with my co-workers I'm trying to create a storage solution capable of doing more than 100k IOPS. See http://jdevelopment.nl/hardware/one-dvd-per-second/ for our attempts thus far.
The problem we're currently facing is that we're unable to get more than ~65k iops for a single device. What we have been trying to do is combining two devices, with each build of of an high performance RAID controller (the 1680IX-12/4GB RAM) with 8 SSDs (mtron pro 7535) on each, into 1 device using either LVM or mdadm striping (raid 0).
In all of our tests the total number of IOPS we get is never higher than ~65k. However, if we put a simultaneous load on the two controllers configured as individual devices, we get a combined total of nearly exactly 100k IOPS (for blocksizes up to 16K, 20 testing threads total, 10 threads per individual device).
Because 65k is 2^16, this number feels like a maximum setting somewhere and not as a hardware limitation. I'm not sure where to look for such a setting though. We're running Debian Linux Lenny. So far I've read up a little on IO schedulers and kernel tuning parameters, but any help would be greatly appreciated.