how many users can Cyrus server support? -- is 5.5 msg/sec sl ow?

[Kendrick Vargas]

On Thu, 26 Sep 2002, Su Li wrote:

> Hi Christian,
> 
> I think you are right. I don't think the bottle neck is Cyrus IMAP. Because
> when I move syslog to the network the performance get 2 times better and
> when I change to a disk striped by 3 disks, I 2 times faster. Right now I
> can get 10 msg/sec. If I can get 15-20 msg/sec, I will be very happy.

You're probably right. We had a production server running sendmail with 
cyrus on a free email service. Because of the way sendmail handled it'd 
queue, sendmail would OFTEN get VERY bogged down with tons of mail. 
Getting hit by a spammer (not in the typical sense, but having the "From" 
address listed as one of the accounts on the machine) OFTEN took the 
machine down. We switched to postfix and the increase in speed was 
dramatic. I never took any detailed statistics, but everything about the 
new setup felt EXTREMELY much faster.

Probably the biggest thing that helped the situation was that postfix
hashes it's queue directory. This made the system MUCH more useable and it
was decidedly better than sendmail's method. With sendmail, the system 
load would go through the roof during a spam attack. With postfix, it 
never goes over .12 or .15. 

You should keep in mind that if you're looking at 20 msg's a second (1200 
msg's per second), your MTA's queing method is gonna make a HUGE 
difference. Unless you hack sendmail to queue differently, your machine is 
gonna take a major performance hit. At that volume of email, you will have 
a high number of undeliverables or errors or what not, and sendmail's 
non-hashed queing system is EXTREMELY under-optimized for such things. 

Furthermore, if you have a bunch of disks, I hope you are doing more than 
simply striping. Striping doesn't do much to increase speed. You wanna do 
something like RAID 5. It spreads your data across all the drives and 
increases the speed of disk operations because bits and pieces of your 
data are comming off all drives at once.

I really think you should look into changing your MTA. Another thing I'm 
not sure about, but I think sendmail writes the message into the queue 
before it attempts to deliver it. Then again, I haven't watched this 
thread to closely so stuff like this might have allready been covered.
			-peace

> 
> Anyways, I got a lot of good suggestions. And now I know Cyrus IMAP can do
> so much better. I'll keep working on it.
> 
> I'll keep you post, as I got some improvement.
> 
> Su
> 
> 
> -----Original Message-----
> From: Christian Schulte [mailto:cs at schulte.it]
> Sent: September 26, 2002 4:20 PM
> To: Su Li
> Cc: 'Lawrence Greenfield'; info-cyrus at andrew.cmu.edu
> Subject: Re: how many users can Cyrus server support? -- is 5.5 msg/sec
> sl ow?
> 
> 
> Su Li wrote:
> 
> >Thanks Larry,
> >
> >But I did "For Sendmail 8.10 - 8.12.3, use the cyrusv2.mc file as a
> template
> >to create a Sendmail configuration file."
> >  
> >
> And this did not increase your performance at all ? If I changed 
> sendmail to deliver directly to the lmtp socket (by socket I do not mean 
> a network socket, I mean the lmtp unix socket!)  I got a tremendous 
> performance increase and I'm totally happy on my Intel PIII with 1.1 GHz 
> and 512 MB of RAM on a RAID5 SCSI array!!! And that all with Solaris and 
> Solaris' very bad performing UFS filesystem! For such a small machine 
> the performance is very very well and I do not understand your problems 
> any more! Maybe you should start thinking about changing your OS to some 
> real BSD unix like FreeBSD, NetBSD, OpenBSD or more commercially 
> Solaris! I'm running all that on a Solaris 8 for the intel architecture 
> and I can't see any performance problems at all (except the UFS 
> performance if writing to the disk but that has nothing to do with cyrus 
> or sendmail. That of course is Solaris specific). I'm monitoring the 
> whole cyrus installation via snmp _every_ day and I do not have any user 
> who talks about performance issues and all are absolutely happy with 
> theire email accounts. Many of them are using IMAP (those who know what 
> that is, are using it happily ;-)) and even my personal account resides 
> on that machine. I have three sendmail installations. One on the same 
> machine delivering through the unix lmtp socket and two others on 
> different machines delivering through the lmtp network socket and all 
> that does really perform quite well. I'm not _the_ poweruser but what on 
> earth are you planning for an installation ? Do you really think that 
> you run into performance problems with 25 msg/sec ? Do you _really_ 
> think that 25 msg/sec is so bad ? 25 msg/sec times 60 are 1500 msg/min 
> times 60 are 90000 msg/hour times 24 are 2160000 msg/day ! Do you really 
> think that your machine will have to handle over 2 million messages 
> _every_ day  ? Isn't that 2 million message think more a peak value on 
> high load situations than the approximately everyday situation ? I think 
> more and more that your problems do not relate to cyrus. Maybe sendmail 
> or even more possible the whole installation (OS, filesystem, the 
> software cyrus depends on) is performing bad and you are trying to find 
> a solution for a problem which relates to a compülete other think than 
> cyrus ? Can you really isolate your problems to cyrus ?
> 
> 
> 
> 
> 
> 
> 

-- 
Let he who is without clue kiss my ass