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jeffcollett

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We are running KMS 6.2.2 on a Xserve with 2 X 2.66 Dual-Core Xeons and 8GB of RAM. We have just under 1200 users and a couple times a week the mail service just seems to bog down and our Que backs up.

Has anyone else experienced this or anything like this?

Thanks
Jeff
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sonofcolin

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Are you using clamav to scan emails? The only time I've seen what you describe is when KMS can no longer connect to clamd. Un-check clamav in the admin console (apply) and then run the que should fix this if it is AV related.
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jeffcollett

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Are are not currently running AV in Kerio because of the performance issue.

Jeff
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My IT Indy

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What sort of drive are you running it on? RAID 5?

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My IT Indy
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jeffcollett

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We have the first 2 drives mirrored. No Raid.

Jeff
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elias

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jeffcollett wrote on Tue, 10 February 2009 11:26

We have the first 2 drives mirrored. No Raid.

You have 1200 users and only 2 drives? Do you have any tools to measure disk IO, specifically disk queue length? That'll tell you immediately if you have a disk IO issue.

Elias
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jeffcollett

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When we watch the disk IO in the activity monitor the write IO is high.

Attached is a screenshot.

Since the disk IO is so high what are my option? Can I install KMS on a raid that is not the primary? To I get faster drives?

Thanks for your help.

Jeff

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elias

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I don't know what you currently have for drives, but you probably need both faster drives and more drives.

In very rough terms, 7200 RPM SATA drive can handle about 60-70 IOs/sec. Whereas a 15000 RPM U320 or SAS drive can handle closer to 150 IOs/sec. Looking at the small graph, it looks like you're sustaining 150-200 write IOs/sec.

In a mirrored (RAID 1) setup, most implementations will balance reads over the two drives, so you can get more read IOs from the array than with a single drive. Unfortunately, the same isn't true for writes since data has to be written to both drives simultaneously.

I don't really have a good handle on how to recommend a disk configuration for 1200 users. If it were me, I'd start with an additional 6 or 8 15k RPM SAS in a RAID 10 array dedicated for just the mail store. With 1200 users, you may need more than that for both performance and capacity, but that's probably where I'd start (it wouldn't surprise me though if you found after some more testing that you need closer to 10 to 12 drives). Keep the existing mirrored drives dedicated for the OS, and also buy a RAID controller that has as much RW cache as you can find.

As I've mentioned in other threads, I only have ~30 users, but we're really email heavy, and it took 4 15k SAS drives in a RAID 10 array dedicated to just the mail store to give me the performance I needed (I started with a pair of mirrored drives and the disk IO completely crushed my server). My RAID controller also has 512 MB of RW cache, of which, approximately 80% is dedicated to writes.

Supporting 1200 users on KMS is not a trivial task and there's no magic answer. It'll take some time and experimentation with different hardware to find the performance you need for the type of mail users you support.

Elias
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My IT Indy

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I would highly recommend using the mirrored raid as your boot drive and put the mailstore folder on an external raid array. eSATA should be fast enough if there are enough drives. You could get one of these with 4x300GB SAS drives in raid 10.

http://eshop.macsales.com/item/Raidon/ST76104SS2PO/

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My IT Indy
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jeffcollett

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The irony is we have the server connected to to an XRaid for our archiving.

We are hoping to off load the Kerio archiving (which is probably our biggest performance issue) to an outside appliance and that will allow is to move our mailstore to the Raid 5 with a 2Gig fiber link and keep our OS on the mirror.

I appreciate everyone's help in working through this with me.

I am curious to know if anyone else is running Kerio with this many or possibly more users.

Jeff
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elias

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jeffcollett wrote on Tue, 10 February 2009 14:09

We are hoping to off load the Kerio archiving (which is probably our biggest performance issue) to an outside appliance and that will allow is to move our mailstore to the Raid 5 with a 2Gig fiber link and keep our OS on the mirror.

You don't want to do that. RAID 5 is not appropriate for a busy KMS and you could find that you actually get worse performance from that setup. The calculation and writing of parity will be detrimental to your server's performance. Your mail store really needs to be on a RAID 10 volume.

Elias
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silver02suby

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Not to jump in and disagree, but Raid 10 (also called raid 1/0) is exactly how we lost a massive amount of data a few years ago. We use a Mac Pro with an external RAID-5 with live hot-spare over SATA-II and KMS screams. Backups are always your friend as well... but we are very happy with our hardware RAID-5.

-Bill
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monsterfreecity

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Given that RAID 1+0 is the most fault-tolerant of all RAID schemes, I'd be curious to hear what led to data loss.

I'm about to implement a six-disk RAID 1+0 using 300GB 15K RPM SAS drives for the store and two smaller SASs for a RAID 1 boot disk...
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jeffcollett

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Well I just finished moving our mail store to a RAID 0+1. We are using a an XRAID with 6 drives. It is flying and yes... The stores are backed up.

Jeff
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