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carlson

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We are proposing to deploy Kerio MailServer imminently, and would appreciate comments regarding best server platform (Linux vs Windows Server) for performance. Our assumption is that Linux will scale to higher performance on the same hardware footprint. True for Kerio? Any other factors to consider?

Second, some of our users have Outlook PSTs in the 4 - 9GB range, and we would like to enable these users to leave all their mail in the future on the server, partly due to data risk of high-value PST silos. How well does Kerio scale with large mailboxes? Is there any slowdown for basic operations, such as check for new mail, sending mail, moving between messages / folders, moving messages, etc.? How well does Search scale with large mailboxes?

Any suggestions for how to deal with large mailboxes appreciated. With PSTs, eventually performance requires archiving old mail into one or more archive PSTs. Curious what to expect with Kerio, and what best practices are when users prefer keeping large mailboxes.

Our user mailboxes are large due to number of messages, extensive inline images in HTML email, and extensive attachments.

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winkelman

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Use the fastest disk subsystem you can afford. I would say at least 10k or 15k RPM SCSI drives, even better would be in RAID-10. Kerio's performance is IMO most dependent on disk speed.

KOC can handle vast mailboxes I'm sure, but I would limit the number of individual mail messages per folder. KOC can be somewhat sluggish handling mailboxes with thousands upon thousands of messages. In my experience only when first opening such folders, but some here report more troubles. Further, copying a few thousand messages from one folder to another (in one go) may also take a few minutes. But that's not something you do on a daily basis, probably. All in all, it's best to instruct your users to file away messages into separate folders and for example copy 'old' mail (let's say mail older then a year) to specific, not often used, 'archive' folders so the active 'working' folders stay manageable. (You could use Outlook's archiving function, but then that mail would not be available on the server anymore.)
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rencorp

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I only ever install Kerio for my customers on SuSE Linux, so here are my experiences with that platform.

For the server, I would go for the best spec you can, but as Winkelman says, the disks do seem to be the overiding factor in performance, so his suggestions on disks sound good to me - as big and as fast as you can get seems to be the rule of thumb.

Most of my customers seem to have mailboxes around 2-3Gb in size, containing around 25,000 - 40,000 messages. Most have between 15 and 30 users. I can get away with running Kerio for these sites on a standard P4 machine, with 512Mb RAM and a pair of 120GB IDE disks - I never seem to have any performance issues at all. Most of the client PC's are better spec than this, but Kerio and SuSE never seem to complain about lack of resources. I like to think that this shows how well Kerio and Linux will scale up. I'm sure there are Windows people out there who have the same feelings - hopefully they can confirm this for you here.

The only problem I can see you might run in to is the migration from the PST files to KOC. Importing a PST file appears to have some inherent issues which have been noted on this forum before. I tend to do the transfer manually using drag and drop/copy and paste methods, as this seems to be able to cope with message properties much better. It does take up a lot of time, so beware.

As for KOC performance, I would say that you should try and keep the size of any frequently used folders down to a minimum. An Inbox with 10,000 items in it will really creak, but splitting that down into a number of sub folders each with only hundreds of messages will have a big, positive impact on the user experience.

Can't think of anything else that might be relevant. I hope that a Windows user posts here as well to give a balanced view of the Kerio world.

Gary
www.rencorp.co.uk

Kerio Certified Business Partner - Messaging
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winkelman

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I run Kerio Mail Server together with Kerio Winroute firewall on Windows Server 2003 R2 on a IBM xSeries 336 server with a single 3.2Ghz Intel Xeon CPU and 1Gb RAM.

I have about 100 active users (90% on Webmail, the rest on Outlook/KOC or IMAP). Mailboxes are between 50Mb and 2Gb. Total mail store is 23Gb and contains 391,000 files. All this is running on two 136Gb 15kRPM SCSI drives in RAID-1.

Currently the full Windows machine uses about 600MB RAM. KMS currently uses only 76Mb (with a peak usage of 140Mb since reboot 76 days ago). The anti-spam process consumes about 210Mb (peak also 210Mb). So in total KMS over here uses at most about 350Mb, mostly due to the anti-spam.

The CPU almost never goes over 20% and normally fluctuates between 10 and 15%. Remember that this is including Kerio Winroute Firewall that inspects and virus-scans traffic over a 50Mbit (up and down) Internet connection. The only thing that gets it to ~35% is the backup process that I scheduled every night (probably the zipping that uses somewhat more CPU).

So yes, IMHO Kerio products use the resources very efficiently.

Since KMS reached 6.1 I never have had any stability problems (KMS before 6.1 was not so stable...). The only time I reboot is when I update Kerio Winroute Firewall (so yes, that happens every other month or so). At that time I will also perform the necessary Windows patches. Currently the server is running for 76 days without a glitch whatsoever.
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winkelman

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Good to know: I did see a dramatic increase in KMS performance when migrating from 72000 RPM IDE drivers (in RAID-1) to the aforementioned 15kRPM SCSI drives... That's why I stressed the importance of a speedy, low latency disk subsystem.
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Nixs

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Unlike some mail servers I have used which utilize databases, Kerio stores each e-mail as an individual file (like *most* mail servers I've seen.)

So you have to also make a decision on block size. If you go with a larger block size for performance (64K for example) then if your users have a lot of small e-mails, each is rounded up to the closest 64K block size.

If you go with a smaller block size (4K) then you waste less space, at the cost of performance. You don't see this issue on small installs, but if you are talking a large number of mail boxes it is an issue.

We noticed that when we went from a 64K block size on our roaming profile directory to 4K, users cookie directory when from hundreds of MB each user to about 20-30MB -- just due to block size.

We have Kerio on Windows 2003 server with two 3GHz processors in Hyperthreading mode. We have 2GB of RAM and three 146.8GB Ultra320 10K SCSI Hard Drive in a RAID5 array with 4K block size. We have about 30 users and I have about 4GB of space used myself, with nearly 100k e-mails. I see no performance issues unless I try to sync everything (all e-mail) up on my phone. When I copied all my files from my PST to Kerio, everything was dated as the current date so downloading 3 days of e-mail resulted in everything attempting to come down.




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winkelman

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I would rather use RAID-1 than RAID-5, especially when the RAID-5 array is made up out of just 3 disks. RAID-1 has faster write performance is is capacity-wise only slightly less efficient than RAID-5 with 3 disks (50% versus 66% effective disk space).

These days hard drives are cheap and big enough to trade off 16% capacity for higher write speeds.

When opting for RAID-5 arrays with more 4 or more disks, you indeed gain effective disk space. But when you can 'afford' that many disks, I'd still not use RAID-5 but go for RAID-10. That's a lot faster...
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