Hi,
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?
The only thing I haven't done from above is to use ionice on mail processes. I'm using RAID5 across three 1TB SATA3 disks, I'm using deadline scheduler, the /var partition is mounted noatime, and the disk is mounted raw: <disk type='file' device='disk'> <driver name='qemu' type='raw'/> <source file='/var/lib/libvirt/images/mail02.img'/> <target dev='vda' bus='virtio'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/> How do I configure BIND to ignore TTLs and keep everything for five minutes, as suggested? Thanks, Alex