Hello, On Fri, 10 Feb 2017 21:59:49 +0530 Rajesh M wrote:
You replied below my signature, making a normal reply/quotation impossible for decent mail clients, which is worse than top-quoting. Please reply in-line or at the top if must be. > thanks christian > > during peak times here are the results for connections > > [root@ns1 domains]# doveadm who |grep imap |wc -l > username # proto (pids) (ips) > 631 > [root@ns1 domains]# doveadm who |grep pop3 |wc -l > username # proto (pids) (ips) > 233 > As Joseph mentioned, these are users, not sessions. And while this gives us some ideas, it doesn't answer my question about login rates. Do something like this: "grep Login: /var/log/mail.log.1 |wc -l" with the mail.log being of a typical, busy day. On my larger servers that average to 35 logins per second, with obviously higher peaks. Without the mail process re-usage (idling), that would have the dovecot master process use about 35% of a decent cpu core, with 100% being a hard limit. > > could you please guide me concerning the dovecot config files settings to > handle the above 631 imap and 233 pop connections. > What do you mean, isn't your current system handling that? See the various tuning, performance hints on the wiki, but w/o more info where your system is stalling, dovecot config changes might not be enough. > number of mailboxes is around 4000 -- some users would consume 25 GB while > others would be just around 10 MB > So that at least puts an upper limit to the users, however w/o quotas your users could easily swamp your storage. And those 25GB mailbox users will have a rather large IMAP mail process memory footprint. > this is a hex core machine with hyperthreading -- so 12 cores > With the exception of that dovecot master forking issue, I've never run out of CPU resources with it. > [root@ns1 domains]# iostat > Linux 2.6.32-431.29.2.el6.x86_64 (ns1.bizmailserver.net) 02/10/2017 > _x86_64_ (12 CPU) > > avg-cpu: %user %nice %system %iowait %steal %idle > 2.67 0.00 0.65 3.43 0.00 > 93.25 > > Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn > sdd 44.95 1094.25 765.10 720884842 504041712 > sdc 1.92 32.15 0.03 21178186 21248 > sdb 34.71 1377.37 625.54 907398402 412102224 > sda 49.88 124.29 2587.32 81879548 1704506408 > > Rather meaningless w/o knowning which drive is which. Also an "iostat -x" oneshot summary and a few samples of when the machine is busy would be vastly more informative. atop is a good tool (when not running with 20k+ processes) to give you an idea about bottlenecks and what resource is being utilized how much. Christian > > thanks > rajesh > ----- Original Message ----- > From: Christian Balzer [mailto:ch...@gol.com] > To: dovecot@dovecot.org > Cc: 24x7ser...@24x7server.net > Sent: Fri, 10 Feb 2017 17:58:58 +0900 > Subject: > > 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: > 1. Login processes themselves (easily fixed by high performance mode) > 2. Auth processes (that will depend on your backends, method mostly) > 3. 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 ch...@gol.com Global OnLine Japan/Rakuten Communications http://www.gol.com/
