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Saturday, August 24, 2019

Exchange Veeam Backup Error 0x800401fd: Unable To Truncate Exchange Logs

We use Veeam to back up our Exchange 2016 environment. It generally works ok; if I had my way (and upper management understood Exchange) I'd run backup-less since we have a DAG and all...but whatever.

Every so often Veeam throws errors, mostly dealing with VSS issues; see my old posts here and here.

Now, I just got a new one, where Veeam finishes the backup job, but couldn't truncate the Exchange Transaction logs, causing the log volumes to get pretty big.

Veeam Error:

Unable to truncate Microsoft Exchange transaction logs. Details: Failed to call RPC function 'Vss.FinishSnapshot': Error code: 0x800401fd. Failed to invoke func [FinishSnapshot]: Object is not connected to server.

Exchange Error:

On the Exchange DAG node that Veeam connects to, there's also the following Application Event 2034:

Log Name:      Application
 Source:        MSExchangeRepl
 Date:          8/16/2019 8:51:56 PM
 Event ID:      2034
 Task Category: Exchange VSS Writer
 Level:         Error
 Keywords:      Classic
 User:          N/A
 Computer:      MBX1.exchangeitup.com
 Description:
 The Microsoft Exchange Replication service VSS Writer (Instance c2f51bd6-b7b3-49e1-8e12-4ad329955268) failed with error FFFFFFFD when processing the backup completion event.


This means our VSS Writer on the Exchange server is malfunctioning.

To check for VSS errors, fire up the CMD on the Exchange server, and run:

vssadmin list writers

You'll most likely get the following:

Writer name: 'Microsoft Exchange Writer'
Writer Id: {76fe1ac4-15f7-4bcd-987e-8e1acb462fb7}
Writer Instance Id: {2e1494ca-6e06-47a8-af0e-f77213bfecaf}
State: [12] Failed
Last error: Retryable error


The Fix:

Luckily the fix is easy!

A lot of forums will say to restart the Exchange Store service. DO NOT DO THIS! That results in database dismounts, and client connectivity loss.

To "reset" the VSS writer properly, restart the Exchange Replication Service (You'll notice the above event references the Repl service). This will not cause any downtime, as its for the database replication across servers.

Open the EMS (Exchange Management Shell) on the Exchange server, and run the following cmdlet to stop the Replication Service:

Stop-Service MSExchangeRepl

Now start it with the following:

Start-Service MSExchangeRepl

Now, let's check the VSS Writers again, and you'll see the error cleared:

Writer name: 'Microsoft Exchange Writer'
Writer Id: {76fe1ac4-15f7-4bcd-987e-8e1acb462fb7}
Writer Instance Id: {12c870b7-b0b2-418c-88c0-3564025eb01c}
State: [1] Stable
Last error: No error


Re-run your backup, or let it run on the next schedule, and you should get a successful backup, with logs truncated!

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