Exchange 2003 Mailbox Size Limits

Posted on 2004-04-05
Last Modified: 2012-06-27

Last fall I installed a new server and Exchange 2003.  All is working great, but I am seeing peoples mailboxes begin to balloon.  Mailboxes have gone from 250 to over 800 meg in the past 6 months.  We are a small company, and we DO have the diskspace and processing power at this point to handle as much as people want to throw at it.  My concern is that as time goes on, poor mailbox maintenance practices become commonplace and that large mailboxes could become troublesome.

Does anyone out there have any information about any performance considerations with Exchange 2003 and large mailboxes?  

Do you have any reasons that larger mailboxes are problematic or arguments for maintaining smaller mailboxes?

Thanks for your help.
Question by:TWFarrington
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Accepted Solution

OneHump earned 150 total points
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Large mailboxes are a big problem.  It's not so much about performance than it is about the time it takes to back your servers up and the time it takes to recover from failure.  This is one of the reasons Microsoft gave us storage groups with multiple stores.  It allows us to break a previously large single database into several smaller databases, increasing the number of mailboxes possible per server.

How big your stores get depend on your service level agreements and the performance of your backup solution.  If you can backup 5G per hour, for example, and customers require their email up within 3 hours of a server failure, then you probably want no bigger than a 10G database.  This gives you a 2 hour recovery time with an hour for preparation and problems.

It is really important to foster a culture in your organization that Email is a not a file transfer/storage solution.  Doing this early on is easier than doing it when everyone has 500M mailboxes.

There are also solutions out there that will archive email older than a certain time to inexpensive NAS boxes.  I don't like that sort of thing because it reindexes the Exchange database to make archived email available to the client seamlessly.  It's a support problem waiting to happen.

In terms of performance, disk configuration and throughput are all that relate when it comes to storage.  Most performance bottlenecks with Exchange 200x are with CPU/RAM/Network.


Assisted Solution

Isigow earned 100 total points
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Also remember,
Maximum size of a single exchange store in Exchange 2k and 2k3 standard is 16GB, beyond that and the store will begin having major issues.
Best soltuion is usually to develop multiple store strategies. Usually something like a Financial store, Administrative store, IT Store work. (obviously depending on company)

That way you can restrict loss and downtime in the event of having to do restores as OneHump said, plus you reduce sizes of individual mail stores.

Dont forget you can also set Exchange up to do warning at certain mailbox sizes, andrestrict access all together at other mailbox sizes. If you've seen major jumps in a short time you may also want to check for virii and/or large attachments sitting in the users mailboxes.
one 5MB movie sent around the office can increase you overall store tremendously if the movie isnt deleted.


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Comment Utility
hrm think I typo'd there, Exchange 2k is 16GB, exch 2003 is 16TerraBytes (with a recommended size for no drop in performance of 16GB)

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Hi good day TW.
you should tell us if you have standard or enterprise, Standard being limited to 16GB the performance impact is not that important, it is more a factor of controlling the Pack rat syndrome, some users are totally in distress if they have to delete an email that is 2 years old. As mentioned above Exchange let you, set the maximum size mailbox easily from active directory for Users on the exchange server or on your machine if you installed the management tools from the exchange setup CD.
 for the standard still I would divide the database in 3 storage group, a small user storage , a Big users Storage and an "untouchable Storage" reserved for the Top Brass, this way you give another level of protection to your users so they have separate database files if one goes down the others are still running and you can do a much faster restore and backup. we are keeping our users to under 300MB by rules, only the Management is exempted, not very fair, is not it? by the way is this common practice in every office? just wondering... anyway i do not know the answer for enterprise but we love to know what best practice is, for exchange enterprise. good day
by the way we are running 50 users on exchange 2003 with an old dual 733Mhz with 1024mb of Ram, a raid that is 30GB, our database is around 10GB and the system is plenty fast...hope it helped a little

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ahh... The standard Exchange limit is 16gig. If you go with Enterprise Exchange the limit of 16 gig is gone.

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Thanks for the additional info.  We are using Exchange 2003 Enterprise.  With the help of you all, I am in the process of setting a standard mailbox limit of 250mb, with exceptions for Sr. Management.  Their feeling is that their time is better used working, than cleaning out their emails, and that if the majority of the users have well managed mailboxes, their larger mailboxes will not signficantly delay a restoral ... and in any case, the restoral delay as a result of their larger mailbox sizes will not be as significant as the time it would take to manage their email.  In our case, I have to agree.  I am also setting up rules on their mailboxes to better handle spam (which is an ever-growing problem), so that they are not keeping that information.  I am also working to educate users on the issue of duplication, and the lack of necessity to store a document received in an email in both the email and externally to the email on the server.

Thanks for all your feedback.

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