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 at ns1 domains]# doveadm who |grep imap |wc -l
> username # proto (pids) (ips)
> 631
> [root at 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 at 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:chibi at gol.com]
> To: dovecot at dovecot.org
> Cc: 24x7server at 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
chibi at gol.com Global OnLine Japan/Rakuten Communications
http://www.gol.com/