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MW-6979 asked YukiSun-MSFT commented

Mailbox exports hugely blown up

Hello exchange pros,

I've been trying to export the mailboxes from my exchange servers (4 servers in the DAG) one database at a time with this command (unlimited baditems is fully intended):

$AllMailboxes = Get-Mailbox -Database "database"
$Path = "\\servername\exportfolder"
foreach ($Mailbox in $AllMailboxes)
{ New-MailboxExportRequest -Mailbox $Mailbox.alias -FilePath "\\$Path\$($Mailbox.SAMAccountname).pst" -baditemlimit unlimited }

The thing is the exports are extremely unreliable. In every batch i have multiple empty PSTs (size = 265kb) but the mailboxes aren't empty and multiple hugely blown up PSTs.

One example:

Size of the PST: 79,5 GB (85.390.615.552 bytes)

Result of Get-MailboxStatistics mailbox| Format-List StorageLimitStatus,TotalItemSize,TotalDeletedItemSize,ItemCount,DeletedItemCount

StorageLimitStatus :
TotalItemSize : 12.8 GB (13,740,861,224 bytes)
TotalDeletedItemSize : 0 B (0 bytes)
ItemCount : 37740
DeletedItemCount : 0

Only a few mailboxes per database behave that way and when i export those mailboxes one at a time, it works fine.

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Hi @MW-6979

In every batch i have multiple empty PSTs (size = 265kb) but the mailboxes aren't empty and multiple hugely blown up PSTs.

Sorry but I got a little confused here, do you mean the empty PSTs and hugely blown up PSTs are generated at the same time? Or did I misunderstand anything?

when i export those mailboxes one at a time, it works fine.

As regards to the mailbox mentioned in the example, do you mean the size of the PST file is much smaller when you export the mailbox separately?


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Hello and thanks for replying.

Sorry but I got a little confused here, do you mean the empty PSTs and hugely blown up PSTs are generated at the same time? Or did I misunderstand anything?

Yes, they are both generated by the same New-MailboxExportRequest. The majority of PSTs have the expected size but around 10% are in the range i described in my first post (6-7 times the size of the Mailbox).


As regards to the mailbox mentioned in the example, do you mean the size of the PST file is much smaller when you export the mailbox separately?

Yes, after i deleted the PST, removed the completed exportrequest and exported the Mailbox as a single job, it is now marked as completed and the PST has the expected size.

I can provide more examples if needed.



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YukiSun-MSFT avatar image
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YukiSun-MSFT answered YukiSun-MSFT commented

Hi @MW-6979,

I tested using the command you shared above and it worked just fine on my end. The size of the PSTs are similar to the actual mailbox size.

But regarding the "empty PSTs (size = 265kb)" issue, I noticed that during the export process, the PST file size of some mailboxes did show as "265kb" for a few seconds and then turned into the final size. After further research, I found the thread below which discusses a similar situaiton. According to the discussion there, we can learn that the PST file size always shows as 265 KB before the exporting process finished.
Export Mailbox to .PST
116148-image1.png
(The screenshot said "256KB", but from the context of that thread, it's likely a typo and it should be "265 KB".)

Therefore, for your situation, it's suggested to check the status of the export request of the problematic mailboxes to see if it has completed:

 Get-MailboxExportRequest <Mailbox>

Regarding the hugely blown up PSTs, I'd also recommend confiming the request status using the command above. Besides, sometims the huge PST file size might be caused by disk latency, so you can consider checking the disk health in case it is related to any disk latency issue.


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Hello,

all issues i reported were from PST exports that were marked as "completed" by the Get-MailboxExportRequest command, so unless this status is unreliable, this is not the issue.

However, there are always many exportrequests that whose status is "StalledDueToSource_" followed by either DiskLatency or Processor. What i understand from your post is that i need to break down the exports into smaller chunks. Currently i am exporting the exchange on a per database base (around 50-60 mailboxes each).

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Hi @MW-6979,

However, there are always many exportrequests that whose status is "StalledDueToSource_" followed by either DiskLatency or Processor. What i understand from your post is that i need to break down the exports into smaller chunks.

For this circumstance, agree with you that it could be an option to break down the exports into smaller chunks if currently it's not easy to detect and repair the issue with the disks.

Besides, based on my experience, it's suggested to removing the old export requests in time as this might lead to the "StalledDueToSource_" as well. In addition, I'd suggest trying providing the export requests with a higher priority and see if there's any improvement. For example, the New-MailboxExportRequest part of the command can be ajusted to below:

 foreach ($Mailbox in $AllMailboxes)
 { New-MailboxExportRequest -Mailbox $Mailbox.alias -FilePath "\\$Path\$($Mailbox.SAMAccountname).pst" -baditemlimit unlimited  –Priority Highest }

Hope it can be helpful.


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Hi @MW-6979,

It's been a few days since we have got an update. Please let us know if the provided suggestion is helpful or if you need any further assistance.


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Hi @YukiSun-MSFT

Sorry for not replying i haven't had the time to test yet. I will run an export with the "–Priority Highest" swich like you suggested and let you know if that brings any improvement. After that i'll try to break down the exports into smaller chunks to see if the problem still persists. I find it unlikely that there are problems with the disks as the problem happens with all four exchange servers in the DAG though they are all on the same storage so i can't rule out completely that there is in fact a hardware problem.

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Hi @MW-6979,

Appreciate it for the response. Just have a go at your convenience and feel free to post back with any update.


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Hello @YukiSun-MSFT

the priority switch didn't show any improvement, 14 out of 40 PSTs where 3x and more the size they should be. I then only exported 10 mailboxes at a time and it worked without a problem. I would still like to know what exactly causes these issues but it's an acceptable workaround.

EDIT: Unfortunately i have to take this back. I exported another 5 Mailboxes and 2 of them were again a lot bigger than they should be. So even breaking it into smaller chunks is unreliable at best.

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Hi @YukiSun-MSFT

just for your info i rewrote the script to only export one mailbox at a time and the error still happened. When checking the progress it just states "copying messages" but the PST is already more than double the size of the Mailbox so it is not an issue of disk latency.

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Hi @YukiSun-MSFT

just for your info i rewrote the script to only export one mailbox at a time and the error still happened. When checking the progress it just states "copying messages" but the PST is already more than double the size of the Mailbox so it is not an issue of disk latency.

What i noticed is that for this export request only, it produced the following message:

119843-2021-08-02-10-04-08-window.png


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