We are currently experiencing performance issue with our Dovecot system which we believe is caused by excessive writes to the dovecot files. The confusing thing is that we are seeing more writes than reads on our Dovecot volume when you would assume that most of the IO should be reads from customers checking their mail.
We're seeing reads vs. writes similar to the following:
# iostat -d 5 -x Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util dm-4 0.00 0.00 485.80 865.80 3886.40 6926.40 8.00 28.69 19.63 0.70 94.00 drbd0 0.00 0.00 485.80 865.80 3886.40 6926.40 8.00 111.42 94.44 0.74 99.60
We can't figure out why we would be seeing twice as many writes as we are reads. Could this have something to do with the index files?
Appreciate any assistance on this issue.