On 8/2/2012 5:39 AM, Stan Hoeppner wrote: > We already gave you the biggest cause of your latency, which is garbage > collection/wear leveling. You can't see inside the SSDs, but you can > see the latency jump with either top (%wa) or iostat (await, > milliseconds). Run > > iostat -x -d 1 20 > > and you get 20 reports 1 second apart. 1s is minimum granularity. This > should clearly show the latency spikes caused by the SSDs. Maybe even > execute it for 60 seconds and pipe to a file. The above assumes Linux can see the individual devices. I've never used Intel's fakeraid. If its driver presents a single device to the kernel instead of both SSD devices, iostat won't show which SSD's garbage collection is kicking in and/or when. It would be most beneficial if you could see the iostat data for both SSD devices as it would tell you exactly when each drive's GC/leveling kicks in. If the Intel fakeraid doesn't allow you to see both devices, you'll need to switch to md/RAID. I'm sure that will be problematic as you're very likely booting from the Intel RAIDed SSD device. -- Stan _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
