Today, I am posting events occurs during Exchange Backup of a Exchange Database in DAG and when backup is taken from Passive Copy of the database. It always makes sense to take backup from passive because that wouldn’t cause any performance impact to live database.
Here is the detail of Database Name – IN-DB-001, It is currently active on EXCH2.LAB.LOCAL and Passive on EXCH1.LAB.LOCAL. We are initiating Full Backup through Symantec Backup Exec. This backup is for Exchange 2010 but this is still relevant to Exchange 2013.
Events on Passive EXCH1.LAB.LOCAL
The backup application gets the metadata for IN-DB-001 from the Exchange Writer, but again, the writer is running in the MS Exchange Replication Service. A new writer instance GUID is generated which will persist throughout the job.
Event 2021 indicates that the backup application, or VSS requestor, has engaged the Exchange Writer. It will appear numerous times throughout the backup as different components are read from metadata, such as log and database file locations.
Events 2110 and 2023 indicate that the backup application has requested a particular set of components to back up, and the backup type.
Note: – Multiple DBs selected on this server will have the same 2110 event on passive server.
Active server EXCH2 is notified that backup of IN-DB-001 has been started.
The replication service for the passive copy’s server signals the active copy server that a backup is in progress. Events 910 and 210 on the active copy server, as well as 960 on the passive copy server.This signify two things:
- They establish which server backing up a passive copy of the database
- The STORE service on the active copy server has marked the database with “backup in progress” in memory and acknowledges that the surrogate backup will proceed.
Events 2025 and 2027 are generated when the replication writer prevents the replication service from writing logs copied from the active copy server to the local disk.
Replay of logs also stops, thereby keeping the contents of the database files unchanged. At this point writes of data for the database getting backed up are “frozen”.
VSS can now create the snapshots in shadow storage for each disk specified in the metadata.
Multiple events will be generated..Each for individual database.
VSS creates snapshots of each disk which holds transaction logs and Database files. Once these complete it signals the Exchange Writer, which in turns allows the replication service to resume log copy and replay. Events 2029 and 2035 are generated when the “thaw” is completed and normal disk writes are allowed to continue.
Once the snapshots are created the backup application can copy blocks of data through VSS, which transfers blocks of data from shadow storage if they’ve been preserved due to a change or from the actual disk volume if they haven’t. The replication service writer waits for the signal that the transfer of data is complete.
When the files necessary for backing up DB1 are safely copied to backup media, the backup application signals VSS that the job is complete. VSS in turn signals the replication writer, and Exchange generates events 963 and 2046 on the passive copy server. The replication service then signals the Information Store service on the active copy server that the job is done, and that log truncation can proceed if all necessary conditions are met. The active copy node generates events 913 and 213 signaling that the surrogate backup is done, and that the database header will be updated with the date and time of the backup.
Events 2033 and 2037 signal the end of the backup. The active copy node flushes and rolls the current transaction log containing database header updates. That log is then shipped and made eligible for replay according to schedule so that the passive database copy is marked with the new header information at the earliest available time. Log truncation also proceeds if possible. In this case the snapshots are destroyed, and normal operations continue.
Event on Active Server:- EXCH2.LAB.LOCAL
Events 910 and 210 on the active copy server
The replication service for the passive copy’s server signals the active copy server that a backup is in progress. Events 910 and 210 on the active copy server.
The replication service then signals the Information Store service on the active copy server that the job is done, and that log truncation can proceed if all necessary conditions are met. The active copy node generates events 913 and 213 signaling that the surrogate backup is done, and that the database header will be updated with the date and time of the backup.
Thank you for reading !