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Exchange 2010: mailboxes+whitespace=database file size?

Posted on 2011-10-14
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Last Modified: 2012-05-12
We have stand-alone Exchange 2010 Version: 14.00.0682.001 on Server 2008 R2 standard, physical machine.

About a week ago, I had to migrate all mailboxes from a previous database on this same machine to a new database because of corruption in one user's outbox that caused the .edb of the previous database to grow out of control (.edb was 463 GB with mailboxes totaling less than 50 GB). I moved each mailbox, choosing not to move corrupted items. Now, only the new database exists.

I've been monitoring the size of the .ebd file each day and comparing it to TotalItemsize + TotalDeletedItemSize + AvailableNewMailboxSpace(whitespace) and noticed the sum of these is not equal to the size of the .edb file. Is that the correct way to determine what the .edb file size should be, or am I missing something? The .edb file has been growing about 300 MB per day for the past few days, so I wonder if the database migration even solved the original problem.

Here's how I'm coming up with the numbers:

GENERATE .CSV OF SIZES OF EACH MAILBOX:
Get-MailboxStatistics -Server “mail02” | Sort -Property TotalItemsize | select DisplayName, LastLoggedOnUserAccount, ItemCount, TotalItemSize, TotalDeletedItemSize, LastLogonTime, LastLogoffTime  | Export-CSV c:\mailboxsizes.csv

GET WHITESPACE OF DATABASE:
Get-MailboxDatabase -Status | Select Servername, Name, AvailableNewMailboxSpace

In CSV, sum of TotalItemsize bytes of all mailboxes = 35,590,476,231 bytes
In CSV, sum of TotalDeletedItemSize bytes of all mailboxes = 15,704,138,000 bytes
AvailableNewMailboxSpace = 234,800,000 bytes
35,590,476,231 + 15,704,138,000 + 234,800,000 = 51,529,414,231 bytes
BUT…
.edb file size=55,709,335,552 bytes. What accounts for the difference?

I have default settings for database maintenance (run daily from 1AM to 5AM, background maintenance enabled, circular logging enabled). I run nightly full backups using Backup Exec 2010.
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Question by:DBrown23
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Expert Comment

by:sunnyc7
ID: 36974998
Run this POSH Script and get a health check + whitespace
http://www.stevieg.org/2011/06/exchange-environment-report/
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Expert Comment

by:Nenadic
ID: 36978881
The extra space is due to other information required for normal operation of the database. This is information that is necessary for data to be written and read as quickly as possible. It includes schema and tables necessary to navigate through the database structure of records.
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Author Comment

by:DBrown23
ID: 36980313
sunnyc7, I attached the output of the script, although it looks like sine I don't have a DAG it didn't provide storage details.

Nenadic, do you know of any documentation that describes details on normal sizes of that "other information"? In my examples, that accounts for about 7% of the total database file size. Here are the updated sizes from this morning:
TotalItemsize bytes of all mailboxes = 35,997,874,371 bytes
TotalDeletedItemSize bytes of all mailboxes = 15,599,797,609 bytes
AvailableNewMailboxSpace = 676,855,808 bytes
.edb file size = 56,246,206,464 bytes
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Expert Comment

by:sunnyc7
ID: 36980441
I wasnt looking for dag in the results. i was looking for information related to online maintenance and if online maint is running according to schedule.

Can you run this from exchange/bin directory

eseutil /ms <edb file name.db>

you can check this article to give you an idea on EDB size.
http://www.msexchange.org/articles/Exchange-Databases-Disk-Consumption.html
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Author Comment

by:DBrown23
ID: 36980612
I'm not sure how to confirm online maintenance is running properly, but the whitespace has been increasing in my examples.

I won't be able to dismount the database any time soon,  so can't use eseutil.
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Expert Comment

by:sunnyc7
ID: 36980683
get-mailboxdatabase | fl *maint*
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Author Comment

by:DBrown23
ID: 36980978
[PS] C:\Windows\system32>get-mailboxdatabase | fl *maint*

BackgroundDatabaseMaintenance : True
MaintenanceSchedule: {Sun.1:00 AM-Sun.5:00 AM, Mon.1:00 AM-Mon.5:00 AM, Tue.1:00 AM-Tue.5:00 AM, Wed.1:00 AM-Wed.5:00 AM, Thu.1:00 AM-Thu.5:00 AM, Fri.1:00 AM-Fri.5:00 AM, Sat.1:00 AM-Sat.5:00 AM}
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Accepted Solution

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Nenadic earned 2000 total points
ID: 36981388
Microsoft's mailbox server storage calculator suggests 20% overhead for database space, so your 7% is actually pretty good. You genuinely needn't worry about this.
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