SBS backup fails intermittently

This is SBS 2008: We've had this problem for many months now. The backup will work fine for 3, 4 or 5 nights. Then it will fail on the following several nights with the message:

"The server backup cannot start because the drive where you want to store the backup is not available. Ensure that any external drives are attached to the server, and then try again."

When I discover that the backup has failed, I can go into backup and go through the motions of recovering data from one of the good backups. This proves to me that the drive is actually available.

After several nights of failed backups, it starts working again without any intervention on my part. I've tried swapping USB devices around, but the behaviour never changes.

A while back I had another problem which may be a factor in all this.... We replaced the USB drives a year ago. After doing so I found that 3 instances of the backup were starting at the same time. I edited the properties of the scheduled task and set it so that fresh instances couldn't start if the task was already running.

Can anyone help please?
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WORKS2011Austin Tech CompanyCommented:
In the backup software what happens if you choose a different drive? I've seen where the next free drive available for example is G: then the next USB uses G: and has issues. Possibly because the drive wasn't disconnected properly. Even if done so I've still seen it fail. After hooking up the USB configure the backup for a different drive letter, something like T:  and let me know.

I'm looking for registry settings that can be deleted that the server saves to connect back to the same device and why the above happens.
TownTalkAuthor Commented:
This is SBS Backup. There is no option to choose a different drive letter. You configure the software to use a particular device and that drive is formatted in a special way and is not given a drive letter. The backup drives are given names instead, and are visible only to the backup software, and are not visible within Windows Explorer.

When the backup runs, it uses whichever pre-configured drive is currently connected to the system. In the past week, the backup succeeded for 4 nights, failed the next 2 and succeeded again last night.
WORKS2011Austin Tech CompanyCommented:
are there any VSS errors reported.
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TownTalkAuthor Commented:
I looked in the Application log at the time the backup failed recently. The failure occured after the backup had been running for 1 hour and 37 minutes. There was a 517 Backup entry:

"The description for Event ID 517 from source Microsoft-Windows-Backup cannot be found. Either the component that raises this event is not installed on your local computer or the installation is corrupted. You can install or repair the component on the local computer.

If the event originated on another computer, the display information had to be saved with the event.

The following information was included with the event:


The resource loader failed to find MUI file"

A few seconds prior to this there were a couple of Event 9782 errors logged:

"Exchange VSS Writer (instance 72c0fac7-4ce1-442b-b83f-ad4f59b374f2:26) has unsuccessfully completed the backup of storage group 'First Storage Group'. No log files have been truncated for this storage group."

Followed by Event 2007: Information Store (3956) Shadow copy instance 26 aborted.

Is it possible that these processes are clashing with each other?
WORKS2011Austin Tech CompanyCommented:
Here's how to check VSS status.

Open an elevated command prompt. Click Start > Run and type CMD, and then click OK.
At the command prompt, type vssadmin list providers, and then press ENTER.
Check the list
Type vssadmin list writers at the command prompt, and then press ENTER.
Confirm that all the VSS writers are showing: State: [1] Stable, No error

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WORKS2011Austin Tech CompanyCommented:
Either with one another or with another application.
TownTalkAuthor Commented:
Vssadmin list provders gives just one entry: Microsoft Software Shadow Copy Provider 1.0

Vssadmin list writers gives a list of 20 writers. They all are in state [5] - waiting for completion.

If this is not correct, then I am surprised because the most recent backup succeeded.
TownTalkAuthor Commented:
When I did some research into this issue, I found some articles saying the problems with Sharepoint could cause problems with VSS writer status. I fixed this, and the VSS Writers are now showing a status of  [1]. But last night's backup failed again saying that the backup device was unavailable.  One wierd thing is that the backup only fails after 4½ hours. If the backup device was unavailable, I would have expected the failure to occur sooner than this.
TownTalkAuthor Commented:
I've fixed it. The clue was staring  me in the face all along. I mentioned a few days ago that at the same time that the backup failed, there were also events being logged relating to a VSS shadow copy of Exchange also failing. I asked at the time if these processes could be clashing with each other.  I rescheduled the Exchange server maintainance so it occured before the backup and both processes are now succeeding.

So whilst we didn't solve the issue in here, your posts were interesting and i've accepted one of them in order to close this thread. Thanks for your help!
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