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How many snapshots does SnapCenter create during the Exchange Backup?

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Applies to

  • SnapCenter Server
  • SnapCenter Plug-in for Exchange

Answer

How many snapshots does SnapCenter create during the Exchange Backup?

SnapCenter creates a different number of snapshots during a backup based on the backup policy.
At this moment (as per product design), SnapCenter creates the following number of snapshots:

  • Policy Full / Full+Log backup with active copy option:

      1 snapshot(vss) on active db volume,
      2 snapshot(vss+log) on active log volume,

  • Policy Full / Full+Log backup with backup on servers option:

     1 snapshot(vss) on passive db volume,
     2 snapshot(vss+log) on passive log volume,
     1 snapshot(log) on active log volume per passive server

  • Policy Log backup with active copy option:

     1 snapshot(log) on active log volume,

  • Policy Log backup backup on servers option:

    1 snapshot(log) on passive log volume,

What is the meaning/purpose of the snapshots with the "_1"  at the end of the name?

The log snapshot are the ones with the name ending with "_1".

There are two kind of log backups. One is created with the full backup workflow. They typically have a backup snapshot with full backup name with an "_1" appended. If the full backup name is "Db1FullPolicy_<timestamp>", the log backup name should be "Db1FullPolicy_<timestamp>_1". One log backup is created by log backup policy. It is the name created just like a full backup name. The UTM for up to full backup setting decides what to retain.

For log backup retention (UTM) in full backup workflow, log backup deletion is global per database; unlike the full backup retention, it is by database per policy.

For the same example as above:

for DB1 policy1 with log UTM 3 count and

policy2 with log UTM 2 count.

When full backup is run for policy 1, the UTM count 3 is applied and we are looking at all the log backups for DB1. So all the log backups for this DB1 older than the 3rd newest full backup for policy 1 are subject for deletion.

When policy2 is run during full backup, UTM count 2 is applied and we are looking at all the log backups for DB1. So all log backups for this DB1 older than the 2nd newest full backup for policy2 are subject for deletion.

Caveat to remember:

During restore, when the full backup (snapshot) is retained and the user wants to do a UTM restore, the log backup snapshot ( _1 ) taken by the full backup workflow is required. So when UTM count is smaller than full retention count and during retention for log backups, we only delete the log backup created by log backup policy and leave the log backup taken in the full backup workflow alone. So for the previous point, when Policy 2 has full backup retention 3 and UTM 2, what we actually delete is all the log backups older than the 2nd newest full backup, but keep the _1 snapshots alone if their full backup snapshot is retained.

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