On Fri, 10 Feb 2017 07:59:52 -0500 KT Walrus wrote:
1500 IMAP sessions will eat up about 3GB alone.
Are you saying that Dovecot needs 2MB of physical memory per IMAP session?
That depends on the IMAP session, read the mailbox size and index size, etc. Some are significantly larger:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1033864 mail 20 0 97600 67m 54m S 0 0.1 0:01.15 imap
But yes, as somebody who has mailbox servers with 55k+ session the average is around 1.6MB.
If I want to support a max 100,000 IMAP sessions per server, I should configure the server to have at least 200GBs of SWAP?
You will want: literally) when doing their obviously flawed cleanup on exit. Some things
- 256GB of real RAM, swap is for chums.
- Understanding how to tune Dovecot and more importantly the overall system to such a task (see that PID up there?).
- Be willing to deal with stuff like top and ps taking ages to start/run and others like atop actually killing dovecot (performance wise, not
clearly do NOT scale well.
My current goal is to have 100k capable servers that work well, 200k in a failover scenario, but that won't be particular enjoyable.
Christian
On Feb 10, 2017, at 3:58 AM, Christian Balzer chibi@gol.com wrote:
On Fri, 10 Feb 2017 01:13:20 +0530 Rajesh M wrote:
hello
could somebody with experience let me know the dovecot config file settings to handle around 1500 simultaneous connections over pop3 and 1500 connection over imap simultaneously.
Be very precise here, you expect to see 1500 as the result of "doveadm who |grep pop3 |wc -l"?
Because that implies an ungodly number of POP3 connects per second, given the typically short duration of these.
1500 IMAP connections (note that frequently a client will have more than the INBOX open and thus have more than one session and thus process on the server) are a much easier proposition, provided they are of the typical long lasting type.
So can you put a number to your expected logins per second (both protocols)?
my server
server configuration hex core processor, 16 gb ram 1 X 600 gb 15 k rpm for main drive and 2 X 2000 gb hdd for data (No raid)
No RAID and no other replication like DRBD? Why would you even bother?
How many users/mailboxes in total with what quota?
1500 IMAP sessions will eat up about 3GB alone. You will want more memory, simply to keep all relevant SLAB bits (inodes, dentries) in RAM.
If you really have several hundreds logins/s, you're facing several bottlenecks:
- Login processes themselves (easily fixed by high performance mode)
- Auth processes (that will depend on your backends, method mostly)
- Dovecot master process (spawning mail processes)
The later is a single-threaded process, so it will benefit from a faster CPU core. It can be dramatically improved by enabling process re-usage, see: http://wiki.dovecot.org/PerformanceTuning
However that also means more memory usage.
Christian
thanks rajesh
[snip]
Christian Balzer Network/Systems Engineer
chibi@gol.com Global OnLine Japan/Rakuten Communications http://www.gol.com/
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Christian Balzer Network/Systems Engineer
chibi@gol.com Global OnLine Japan/Rakuten Communications
http://www.gol.com/