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Reseeding a Failed Database Copy in an Exchange Server 2016 Database Availability Group

When you’re operating an Exchange Server 2016 database availability group you’re going to eventually encounter a failed database copy. The most likely cause is a storage hardware issue, but there are many other ways that database copies can fail.

A failed database will show up in the output of Get-MailboxDatabaseCopyStatus, for example:

Running the command yourself is useful but not very proactive. If you don’t have a monitoring system in place that can detect failed database copies then you can use my Test-ExchangeServerHealth.ps1 PowerShell script to keep an eye on things for you.

Recovery is a manual process if you are not using Autoreseed in your deployment. Once you’ve fixed the underlying issue (e.g. replaced the failed disk) you can reseed the database copy.

If the database and log paths on the server you’re reseeding to already contain files you can add the -DeleteExistingFiles switch to overwrite them.

Also, by default the source for the reseed will be the database copy that is currently active. If you’d prefer to reseed from a different server that may be closer, and therefore faster to reseed from, then you can add the -SourceServer parameter as well.

The duration of the reseed operation will depend on the size of the database and transaction log data that needs to be copied across the network to the server.

After the reseed is complete the database copy should be back to a healthy state and will resume continuous replication.

Paul is a Microsoft MVP for Office Servers and Services. He works as a consultant, writer, and trainer specializing in Office 365 and Exchange Server. Paul is a co-author of Office 365 for IT Pros and several other books, and is also a Pluralsight author.
Category: Exchange Server

2 comments

    • Each database can seed/reseed one copy at a time.

      If you have one database, say DB1, you can seed one copy of that database at a time. If you have 4 copies of DB1, you need to seed or reseed each of them one at a time.

      If you have two or more databases, say DB1 and DB2, each of those databases can seed a copy at the same time.

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