Q

The best ways to recover from a failed server

You can pull out the big guns to manually remove what's left of your failed Exchange Server from Active Directory, but it's best to consider potential alternatives before doing so.

One of our Exchange Servers is permanently down and I'm trying to remove it from our site. After right-clicking the failed server and selecting All Tasks > Remove Server, I get an error that says it can't be removed because people are using mailbox stores on it, even though all end users already moved to a different server. How can I fix this?

While it's possible to pull out a "bigger hammer" and manually remove the remnants of your Exchange Server from Active Directory (ADSI Edit, for example), I would suggest considering a few alternatives.

It's possible that the error you're getting could be resolved by searching for mailboxes that were created -- but that end users never actually logged on to -- and then removing the Exchange attributes. This is a common cause of the symptom you're having. In Exchange 2000/2003, search user objects with Active Directory Users and Computers (ADUC) to find the "Exchange Home Server" attribute for the failed server. In Exchange 2007 and higher, use the Get-Mailbox cmdlet to find any mailboxes on a server or database you may have missed. If you're in a multi-domain forest, don't forget to add the IgnoreDefaultScope parameter so mailboxes from all domains are also displayed.

Even if this eliminates the error you're seeing, I'd caution against manually removing the server. In addition to protecting data on the server (although it sounds like you were able to do so), the services the server was responsible for could include mail flow, client access and system-level functionality. Manually removing the server could cause significant problems if you don't fully transfer all functionality to another server.

The good news is that since the release of Exchange Server 2000, every Exchange Server's configuration information is stored in Active Directory. The configuration data is replicated to every domain controller (DC) in the forest. This centralized and hopefully redundant data set (two or more DCs required) effectively commoditizes the actual Exchange Server hardware. Setup provides a recovery option, which can be used to install Exchange on new hardware while still maintaining the existing server name and services associated with the failed server.

Exchange 2007 and 2010 Setup /m:RecoverServer http://technet.microsoft.com/en-us/library/aa998656(v=EXCHG.80).aspx
Exchange 2013 Setup /m:RecoverServer http://technet.microsoft.com/en-us/library/dd876880(v=exchg.150).aspx

The mailbox databases on the failed server would need to be recovered from backup if the storage subsystem went down with it. You could use Recovery databases, Dial tone portability and database portability to minimize recovery time.

The following table is a reference for where information is stored in AD that would need to be manually removed if you had to do so.

AD Configuration CN=Configuration [domain] -> CN=Services -> CN=Microsoft Exchange -> CN=[organization] -> CN=Administrative Groups -> CN=Servers -> [failedserver]
Mailbox Databases CN=Configuration [domain] → CN=Services → CN=Microsoft Exchange → CN=[organization] → CN=Administrative Groups → CN=Databases [failedserver_databases]
Security Group membership
  • Exchange Server
  • Exchange Trusted Subsystem

About the author:
Richard Luckett is a consultant and instructor specializing in messaging and unified communications. He's been a certified professional with Microsoft since 1996 and has 20 years of experience in the public and private sectors. He's a Microsoft Certified Trainer with more than 15 years of training experience with the Microsoft product line and received the Exchange MVP award in 2006, 2007 and 2008. He's also an expert in deploying and integrating Exchange Server and Lync Server. He leads the Microsoft training and consulting practice at LITSG

Next Steps

For more information about how to recover failed servers, visit this content to get some tips on dealing with the recovery and how to rebuild a failed server.

This was first published in August 2014

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