We are making good progress building a mail server. The server is a KVM
running CentOs 8.2 with vcpus=2 and ram=4GB. The system is under heavy
load and is likely limited by disk performance. The load is generated by a
second KVM using SMTP to send email. Everything seems to be working except
there is nothing in /var/log/maillog for a period of 3 minutes. I'm not
sure what is causing the omission of logs and how to correct this issue.
I'm concerned that we are not following this recommendation, "Don't
overwhelm the disk with mail submissions. Optimize the mail submission rate
by tuning the number of parallel submissions and/or by tuning the Postfix
in_flow_delay parameter setting." There is no indication in
/var/log/maillog of problems (other than 3 minutes of missing logs). I do
not know if "overwhelming the disk" would lead to shutting down data going
to the maillog altogether. I will set in_flow_delay = 2s for this KVM mail
server this evening.
The performance snapshots below seem to show: cpu load average is not
heavy, plenty of ram free, no swapping (stable at 108Mi), dm-0 is working
hard at 129 tps and postfix seems to be keeping up with the load with 39-50
emails in the queue. This run started at 03:05 and created two minutes of
data in /var/log/maillog -- and then nothing for 3 minutes starting at
03:07. I am certain the email in the missing three minutes was actually
delivered or I would be seeing lots of negative feedback from our
subscribers.
>>>>> 03:07:04 up 17:31, 0 users, load average: 0.42, 0.26, 0.10
total used free shared buff/cache
available
Mem: 3.7Gi 832Mi 2.0Gi 101Mi 931Mi
2.5Gi
Swap: 1.0Gi 108Mi 915Mi
Device tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-0 129.00 0.00 2373.50 0 4747
incoming/active queue:
T 5 10 20 40 80 160 320 640 1280
1280+
TOTAL 39 39 0 0 0 0 0 0 0 0
0
gmail.com 8 8 0 0 0 0 0 0 0 0
0
att.net 7 7 0 0 0 0 0 0 0 0
0
bellsouth.net 7 7 0 0 0 0 0 0 0 0
0
sbcglobal.net 7 7 0 0 0 0 0 0 0 0
0
aol.com 4 4 0 0 0 0 0 0 0 0
0
icloud.com 4 4 0 0 0 0 0 0 0 0
0
yahoo.com 1 1 0 0 0 0 0 0 0 0
0
outlook.com 1 1 0 0 0 0 0 0 0 0
0
deferred queue:
T 5 10 20 40 80 160 320 640 1280
1280+
TOTAL 1 0 0 0 0 0 0 0 0 0
1
icloud.com 1 0 0 0 0 0 0 0 0 0
1
>>>>> 03:07:11 up 17:31, 0 users, load average: 0.36, 0.25, 0.10
total used free shared buff/cache
available
Mem: 3.7Gi 858Mi 1.9Gi 101Mi 933Mi
2.5Gi
Swap: 1.0Gi 108Mi 915Mi
Device tps kB_read/s kB_wrtn/s kB_read kB_wrtn
dm-0 121.50 0.00 2326.00 0 4652
incoming/active queue:
T 5 10 20 40 80 160 320 640 1280
1280+
TOTAL 56 56 0 0 0 0 0 0 0 0
0
gmail.com 13 13 0 0 0 0 0 0 0 0
0
att.net 11 11 0 0 0 0 0 0 0 0
0
sbcglobal.net 11 11 0 0 0 0 0 0 0 0
0
bellsouth.net 9 9 0 0 0 0 0 0 0 0
0
icloud.com 6 6 0 0 0 0 0 0 0 0
0
yahoo.com 5 5 0 0 0 0 0 0 0 0
0
rocketmail.com 1 1 0 0 0 0 0 0 0 0
0
deferred queue:
T 5 10 20 40 80 160 320 640 1280
1280+
TOTAL 1 0 0 0 0 0 0 0 0 0
1
icloud.com 1 0 0 0 0 0 0 0 0 0
1
Thanks, Greg
