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Exchange 2000 Standard 16GB Limit - Inconsistencies?

Posted on 2004-08-11
Medium Priority
Last Modified: 2012-06-27
As of late we have been running up against the 16GB limit imposed on the mail store by Exchange 2000 Standard.

When I look at Exchange system manager and tally the sizes listed for all of the mailboxes the total I get is around 2.6GB.  Yet with increasing frequency I hit this wall.

Question:   Is Exchange system manager unreliable with regards to guaging the size of a mailbox?

Additionally we've moved several mailboxes to another Exchange server then run eseutil defrag.   Don't ever seem to recover more than 1GB of space.

Question by:scpeacock
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Expert Comment

ID: 11777956

Info probably coming in two posts -

The capacity limit for a Microsoft Exchange Server server-based Information Store is 16GB. This could be all in one folder, or split up among many folders. A Microsoft Exchange Server generally hosts one Private Information Store (16GB for all Mailboxes), and one Public Information Store (16GB for all public folders).

Personal Folder stores have a theoretical maximum of 2GB total storage. This could be all in one folder or split among many folders. The limit to the number of messages (objects: messages, folders, files, etc.) in a Personal Store is 16K.

A Microsoft Exchange Server can be configured as a private only, public only, or public/private Server. There is a limit of 16GB on any Microsoft Exchange Server for the private database (DB) and a different 16GB limit for the public DB. Therefore, a public/private Microsoft Exchange Server can house 32GB of storage, 16GB of which is for the private DB and the other 16GB for the public DB.

If you have a large Public Folder, you can dedicate a single Microsoft Exchange Public Folder Server to house the data for that one Public Folder, so the limit for the size of a single Public Folder is 16GB.

Microsoft Exchange performs single instance storage in the database on a Microsoft Exchange Server, so the 16GB limit on the private database is really a much larger logical storage. Single instance storage means that if 1000 users on a Microsoft Exchange Server get the same message, the message is only stored once in the database and each of the users gets a pointer to the message. The same single instance storage also holds for attachments. If a user opens their copy of a message and modifies it but they don't modify the attachment, Microsoft Exchange doesn't resave the attachments, just the new message body.

The Microsoft Exchange beta sites saw at least 3:1, and sometimes upwards of 6:1, single instance storage rates because most messages have an average of between 3 and 6 recipients. To extend this, the logical storage limit for users on a single Microsoft Exchange Server is at probably least 16GB*3 and possibly upwards of 16GB*6.

Another factor to consider is how many people use Personal Folders (.PST files) as their delivery store. If users are using Personal Folders, the Microsoft Exchange Server can handle more users. The time at which the limit is reached for storage in the private DB on a specific Microsoft Exchange Server will depend on the pattern of usage by the users.

By default Microsoft Exchange sets up circular logging on the Directory service and the private and public DB's. What this means is that as the transaction log files get flushed to the databases, they are deleted. The beta sites saw, on average, no more than 4 logs files, each of which was MB. So in the default install configuration, log file growth will not be a factor. If an administrator configures their Microsoft Exchange Server not to use circular logging, the log file growth will be based on the number of transactions that are occurring on the Microsoft Exchange Server. This is based purely on activity.

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Accepted Solution

BNettles73 earned 375 total points
ID: 11778034

I read this elsewhere -

You should also get everyone to delete from their mailbox & empty their deleted items folder. If you have Deleted Item Retention set, consider reducing the number of days for retention.  Let the ISMaint (Online defrag) complete a cycle or 2. This process does garbage collection which actually scavages the deleted items past retention and purges them from the database. You should find Info events in the App log in the 700 range showing the starting, & completing. If you see events indicating interruption and never find a completion, it didn't finish the cycle.

Then do an OFFLINE defrag using eseutil /d /ispriv. This type of defrag will shrink the actual file size down. Usually this is done when the drive is critically low on physical space and the database file is "bloated" with white space.

You could also ExMerge all of your data to an alternate location in PSTs and then blow away the database. Create a dialtone database and then Import the data back after you have defrag'd the drive ... this would start with a clean database but obviously would entail more work. You should definitely try to understand the implications prior to heading down this path.

FYI - I have about 400 users per mailbox store spread over 20 servers with 75MB limits per user and my databas databases typically run about 40-45 GB ... defragging doesn't necessarily mean it will completely compress ... you should make sure the daily maintenance is running also to ensure the whitespace is cleaned up.
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Expert Comment

ID: 11778040
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Author Comment

ID: 11778529

Microsoft Knowledge bases states that the /ispriv switch is not available with eseutil in Exchange 2000?  True?

Daily maintenance is running.

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Expert Comment

ID: 11778578

True ... you have to specify the direct path to the database ...
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Expert Comment

ID: 11778585
sorry ... still getting out of the 5.5 mentality myself

Author Comment

ID: 11786298
i've run eseutil /d (offline defrag).   only recovered about .3GB.   Still dangerously close  to the 16GB limit.

By my count through system manager the total sum of the mailboxes is about 2.5GB.

I am assuming that the rest is "white space"?

Is there something else I need to do to compact priv1.edb and priv1.stm?

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Expert Comment

ID: 11786507
If you have enough disk space ... you could try running the eseutil with the /p switch ... this creates a new database and also gives you the ability to switch back to the old database if need be ... I'm not sure if it will do what you want but in theory if it creates a new database then the whitespace should be cleaned up and the database further compacted ... <Just an idea but make sure you get a good backup first!>

Oh ... and while I'm thinking about it ... check out this article ... it has links to just about everything you want to know about defrag'ing Exchange databases ... it also tells you how to get your store mounted if you reach the 16GB limit ....


How many users do you have ... what is your deleted item retention set for ... and do you have mailbox storage restrictions set?

Author Comment

ID: 11786857
Approximately 50 users.   45 are using .pst files.   5 store their mail on the server.

Of the five on the server, three have large mailboxes (900MB, 450MB, and 350MB).

I changed deleted item retention today from 2 days to 0 days.

Storage restrictions are not in effect.    The five users who have their mailboxes on the server are executive types who insist on no restrictions.  As I said above, everyone else uses a .pst file.

I have a new Exchange 2000 Standard server that I planned to use specifically for these heavy duty users.  However, I am experiencing mail delivery latency issues (mail sent from box on old server to new server takes several hours).  This issue is the subject of another thread I've started called "Delay In Delivery to New Exchange 2000 Server."

Author Comment

ID: 11805388
I ran eseutil /p on the mail store.

I got the following results:

Integrity check successful.

  It is recommended that you immediately perform a full backup
  of this database. If you restore a backup made before the
  repair, the database will be rolled back to the state
  it was in at the time of that backup.

Operation completed successfully with 205 (Unknown Error, Unknown Error) after 1312.672 seconds.


The size of the mailstore is exactly the same as before this operation (combined priv1.edb and priv1.stm are about 16.1 GB).

We've cleared a great deal of data from the mailboxes.  There should be nowehere near 16B in the mailstore.  

The .ebd file has remained the same size since the last time we ran the offlne defrag (eseutil /d).   The .stm file is still inscreasing about 10MB per day.

Author Comment

ID: 12292148
We were never able to recover the "white space" with the offline defrag.

Ultimately we:

1) exported all mailboxes to .pst files on their respective client PCs.
2) stopped the information store service.
3) backed up mdbdata directory and then deleted all of its contents.
4) restored pub1.edb and pub1.stm
5) restarted the information store service.
6) remounted the mailstore.   exchange says it will recreate priv1.
7) imported the data back into the mailboxes from the .pst files (all but a few were using .pst files so this wasn't a big deal).

The size of the two priv1 files are now more consistent with what exchange system manager says we have.

Author Comment

ID: 12292159
the mailboxes don't show up in exchange system manager until a message is sent to all of the users.   this should be step 6.5.

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