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tiredofnick

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So I've installed and gotten everyone in the company I work for switched over to Kerio mail server. All clients are on mac os, and we're using ical for caldav integration got around 70 users.

During the day the server will become unresponsive at times, seemingly because it is under too much load. Really though, its not that much load, stats show it is not really under serious load, IMAP connections top out at around 119 connections...

users have also seen the kerio sync connector regularly time out and often fail.

i guess what i'm asking is if anyone has any optimization tips. I am so far extremely disappointed at the performance of Kerio. also, any recommendations on the amount of RAM I should have available for that many users??

the box its installed on is a centos box with an amd opteron 64-bit chip
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sedell

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A bigger factor than RAM or CPU, is the speed of the disks. Most here have found that the faster your hard drive subsystem is, the better. CPU speed and amount of RAM aren't really an issue as long as it's enough for the OS to run smoothly. When you do a performance check on the server, monitor disk activity. It could be that's where your bottleneck is. If it's bad enough, you could see timeouts, failed transfers, etc.

Another issue that could cause that is real-time scanning of the message store by your Anti-virus software. Make sure that store directory is excluded.

Scott
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tiredofnick

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antivirus isn't even on, our firewall takes care of the spam/virus filtering.

the disk thing is interesting though, could be that because we set the OS disk to be a mirrored set that its slowing it down... thanks for the tip!

[Updated on: Fri, 10 October 2008 17:36]

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Eberhard

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Maybe you experience the "Nagle Delayed Acknowledge Problem", it is worth a test.

Responsible is the server, both Win XP and Win 2003, and also on Mac platform.

http://www.stuartcheshire.org/papers/NagleDelayedAck/

One routine tries to optimize the network traffic by bundling packets, the other routine waits for more packets to send fewer response packets, and so in some cases client and server wait 30 times more than neccessary, which slows down the communication by this factor.

To see if this problem persists simply send a 10 MB attachment to your mailserver. If the message needs more than a few seconds to leave outbox you may have it.

For Windows:

HKLM/System/Current Control Set/Services/TCPIP/Parameters/Interfaces/[here choose your LAN]
and add a new DWORD TcpAckFrequency with value 1. You have to reboot the server then!

Then do another attachment sending test.
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winkelman

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Have a look at disk monitors, see if disk operations are queuing up. Disk speed is the main reason of slow KMS performance. I would even go so far as saying it's the ONLY reason of KMS slowness.

Some tips:
go for SCSI/SAS (better at concurrent ops), not SATA/IDE
go for 15.000RPM disk (you want low latency access, throughput performance it not so important for Kerio)
don't use RAID-5 (not so good write performance). Go for RAID-10 or RAID-1.

Can't afford the above? Then sell some RAM, exchange the CPU for a cheaper model and try again Smile
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tiredofnick

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thanks for the tips, can you guys recommend a good disk monitoring utility?
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