On 1.2.2013, at 19.00, Jan-Frode Myklebust janfrode@tanso.net wrote:
We upgraded our two dovecot directors from v2.0.14 to dovecot-ee 2.1.10.3 this week, and after that mail seems to be flowing a lot slower than before. The backend mailstores are untouched, on v2.0.14 still. After the upgrade we've been hitting process_limit for lmtp a lot, and we're struggeling with large queues in the incoming mailservers that are using LMTP virtual transport towards our two directors.
I seem to remember 2.1 should have a new lmtp-proxying code. Is there anything in this that maybe needs to be tuned that's different from v2.0 ? I'm a bit scheptical to just increasing the process_limit for LMTP proxying, as I doubt running many hundreds of simultaneous deliveries should work that much better against the backend storage..
Hmm. The main difference is that v2.1 writes temporary files to mail_temp_dir. If that's in tmpfs (and probably even if it isn't), it should still be pretty fast..
Have you checked if there's an increase in disk I/O usage, or system cpu usage?
Or actually .. It could simply be that in v2.0.15 service lmtp { client_limit } default was changed to 1 (from default_client_limit=1000). This is important with the backend, because writing to message store can be slow, but proxying should be able to handle more than 1 client per process, even with the new temporary file writing. So you could see if it helps to set lmtp { client_limit = 100 } or something.