Re: [libvirt-users] Performance tuning questions for mail server

> This mail server does manage a lot of mail per day, but not enough to > even consume the 8GB I've allocated, and the "mailq" command typically > takes a few seconds to respond, even when there's only a few messages > in the queue. > > iotop may report as much as 2M/s on the host, with an average of about > 400-600K/s. Does that seem like a lot? I can write like 80MB/s at > least using dd to test. I had similar problems previously. The crux in my case is the number of IOPS possible. 100K of 2KB file writes is still 2MB/s but requires a lot more IO overheads than 1 single 2MB file. Recommendations that I was given which stopped the system from locking up included 1. use ionice on the mail process 2. change the IO scheduler/elevator from the default CFQ 3. switch from file-based virtual drives to raw disk devices 4. mount filesystems with noatime Also, are you using RAID 5?