Do you rely on pt-diskstats from Percona Toolkit instead of the standard iostat a lot? There appears to be a nasty bug in pt-diskstats 2.1, which makes it produce bad results.
I noticed some of the numbers I was getting weren’t right, so I tried running iostat and two different releases of pt-diskstat side by side. Here’s what I got:
I can understand the slight differences between the lines in iostat and pt-diskstats 2.0 as they probably weren’t reading /proc/diskstats contents in the same moments, so the values they were seeing could be a bit different. However both lines practically show the same thing.
On the other hand, the line based on the pt-diskstats [Read more...]