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Exchange disconnecting VHD

Posted on 2013-05-15
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Last Modified: 2013-05-17
I have a SBS 2011 server which attaches to a VHD.  This has been operating without a problem to date.  Yesterday I had to move some old mailboxes off the Exchange Mailbox database so I created a new database on the VHD and ran a move request on the Users mailboxes.

It maybe coincidence but once the mailboxes moved the VHD was dismounted.  I ran the mount script and it mounted and then again within a minute or so it dismounted.  I tried via the GUI but the same problem occured.
I'm not how Exchange could force a dismount of the VHD but it seems something is.

The VHD is located on a NAS drive.

Thanks
Graeme
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Question by:TMS
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by:strivoli
ID: 39167362
Do any Warning/Error entries in the Windows Application and/or System logs help?
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Author Comment

by:TMS
ID: 39167621
I see three erros.  2 x Event ID 15 : Device not ready for access.  1x Event ID 15 : Filter Manager failed to attach volume.

I tried again to get the errors and the file mounts and I can then see it and access the volume in Windows Explorer.  Then the volume unmounts.
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Author Comment

by:TMS
ID: 39167672
Just saw this answer but I am not sure what it means.

ID: 38921769
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Author Comment

by:TMS
ID: 39168148
Ok, I managed to find another error under the Exchange log and it says the edb file is missing.  I managed to look in the vhd folder just befor it disconnected and I couldn't see it.  I think this may have been caused by Backupassist running a mailbox backup as the move request was in process.

Not sure why the vhd disconnects but this maybe the cause.

I guess I should use Eseutil / R to recover.  Is this correct or should I follow a different procedure?
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by:strivoli
ID: 39168190
I would firstly stop Backupassist. Consider starting it again when everything is fine and the move process is over.
As per the Eseutil: I thought your issue was only related to the dismount of the VHD. But, what you wrote on your last post makes me believe that you also lost the EDB file "hosted" on the VHD. Is this correct? If this is it, where are the logs located? You can recover if the logs aren't lost (too). Let me know.
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Author Comment

by:TMS
ID: 39168310
Well, I don't know if the two are related.  All I know is I started a move request last night that was almost completed when I left it.  In the morning I saw the problem and the VHD wouldn't stay mounted.  The backup if the mailboxes showed as failed.  I now see the issue with the edb file so I assume BackupAssist failed backing up mailboxes that had moved and somehow the edb file was deleted.  As to why this forces the VHD to unmount I am unsure.  When I do mount the VHD it says it is healthy.
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by:strivoli
ID: 39168337
Is there any AntiVirus running real-time scan? If yes, is it possible that you excluded the original EDB files from real-time scans but did not exclude (new) EDB files hosted on the VHD? If this is it... the AntiVirus might have found infected elements inside the new EDB and moved it to Quarantine (or even deleted the file).
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Author Comment

by:TMS
ID: 39168370
Very good thinking.  Yes, I run AVG and didn't exclude the new path.
Ill exclude and then run a recovery.
Thanks
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Author Comment

by:TMS
ID: 39169634
Ok, I have spent a few hours on this and the common factor is that as soon as I try to copy or zip or run eseutil on the mail.edb file, the vhd disconnects.  It's fine as long as nothing tries to read the file.

So my problem become how does one recover a edb file if the eseutil fails?  If it is irrecoverable then can I just delete the mailbox db from Exchange and then recreate the mail boxes and import the pst files?
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Author Comment

by:TMS
ID: 39169672
Simpler question, is there a recovery procedure if the edb file is corrupt.  The move request was to a new Mail database.  All the logs seem to be there and the .jrs files.  There is also a catalogue folder.
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strivoli earned 500 total points
ID: 39170518
Your scenario is a little complicated and I don't want to give any suggestions that might make things even worst.
I'll tell you what I would do:
a. Understand why the VHD disconnects as soon as there is a little of I/O:
i. Did you run CHKDSK on the Logical Disks hosted by the VHD?
ii. Is the System fully patched with Microsoft Update? Perhaps there's a fix to this strange "VHD disconnection" issue.
iii. Did you try to, temporarily, disable Real-Time AV and access the EDB file using eseutil? Perhaps the AV is interfering with the I/O on the VHD. WARNING: remember to re-enable AV after this test is over.
iv. The NAS drive is connected over a LAN @100Mb or @1Gb?
v. Is there any newer driver for the NIC (which is used to connect to the NAS)?
vi. Is the NAS fully patched (or better, is there any update available for the NAS)?

I know these are many questions but I need the answers in order to give you further suggestions. Thank you.
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Author Comment

by:TMS
ID: 39171145
Thanks for your reply.  I ended up deleteing the edb file and Exchange recreated it and email flowed to my mailbox.  However, it seems the same problem then occured and the vhd was dropped.  This morning I couldn't access the NAS and someone on site confirm the NAS drive had a system failure light flashing....  So, I'll see what I can find on the NAS drive tonight but clearly there would seem to be an issue there as you summised.  The drive had been fine as it was being used for backups.  Not sure I'll find out if the problem was caused by a NAS error or if there was a problem with the VHD that caused the problem with the NAS.

Will respond later with an update.

Thanks
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Author Comment

by:TMS
ID: 39173231
I spoke to EMC and it seems one of the disks failed.  It has a RAid 1 setup so i have removed one disk as advised and the device is now running a startup check which may take some time as it is 2T.

The EMC devices support hosting iSCSI drives.  When I get this back to normal would it be better to run iSCSI from the NAS drives or continue to use Windows 2008 to create Vhd drives on the NAS?  They appear to be similar to me but wondered if one was more reliable?  Main issue is startup as I use a startup script to make the connection which can at times fail. Would the iSCSI initiator be more reliable for auto mount?  Also, if the router restarts during the day then the VHD is dropped.  Would the iSCSI initiator reestablish the connection in this situation?

Sorry for all the questions.  I'll mark your previous reply as the solution.

Cheers
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by:strivoli
ID: 39173854
Your questions, my answers:

would it be better to run iSCSI from the NAS drives or continue to use Windows 2008 to create Vhd drives on the NAS?
I would choose the iSCSI instead of a VHD. The next question/answer might explain better why.

They appear to be similar to me but wondered if one was more reliable?
The result is quite the same (it is more than similar): obtain disk space from the NAS and make it available to the server. I think they are both equally reliable in ideal conditions (hardware working, complete patching, and so on) but I would choose iSCSI instead of VHD because it's more "direct" (has less layers) than the VHD approach.

Would the iSCSI initiator be more reliable for auto mount?
It should be even though testing deeply is the only secure way of discovering it.

Would the iSCSI initiator reestablish the connection in this situation (router restarts during the day)?
Yes, it should. I would spend some words on this issue. An iSCSI connection should be persistent and as a result all devices involved should work 24x7 including routers. If the router needs restarts during the day and it is crucial for your iSCSI link, investigate why that is needed and make it work 24x7.

Have a nice day!
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Author Comment

by:TMS
ID: 39173928
Thank you very much.  Points noted.

Router restart has been required because it seems the UDP DoS was reaching its threshold so stopping NAT routing for HTTP traffic.  I think this is now resolved so hopefully less of an issue.  However, I was thinking to look at moving the VDSL router so that it is not the main router.  Need to do a bit of reading.

I like the VHD concept but I prefer reliability..  I use it at another clients site and it has been faultless but they are smaller.

Thanks again.  It's Friday so have a good day and weekend.
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