Administrator Guide

2. The primary group increases the replica reserve if the replica volume usage increased since you enabled replication on the
volume.
NOTE: If delegated space is too small to hold the increased, replica reserve, the primary group generates an event
message and replication pauses. Replication resumes automatically when delegated space is large enough to hold
the reserve.
3. The primary group copies the contents of the volume to replica reserve, decreasing the amount of free replica reserve. For
example, if the volume consists of 10GB of data, free replica reserve decreases by 10GB.
At this point, the replica reserve contains one replica, which is the most recent, complete replica.
Replica Reserve Usage – Subsequent Replications
1. The primary group determines how much volume data to replicate. For replication operations other than the rst, the primary
group copies only the data that changed since the previous complete replication (the deltas).
2. The primary group increases the replica reserve if the replica volume usage increased since the previous replication operation.
NOTE: If delegated space is too small to hold the increased, replica reserve, the primary group generates an event
message and replication pauses. Replication resumes automatically when delegated space is large enough to hold
the reserve.
3. If not enough free replica reserve is available, the system tries to borrow space to t the new replicas. If any objects are
borrowing space, they might be deleted to make room for the new replicas. Also, borrowing can provide more space, but only
temporarily. Replicas could still be deleted.
The most recent, complete replica is never deleted automatically, ensuring that you always have a current copy of volume data
on the secondary group.
4. The primary group copies the volume data to replica reserve, decreasing the amount of free replica reserve. For example, if the
replication transferred 5GB of new data, free replica reserve decreases by 5GB.
To make sure that replication operations complete and keep the desired number of volume replicas, it is important to allocate
sucient delegated space and specify the correct replica reserve percentage. The amount of delegated space that you need
depends on the replica reserve requirements for all the replicated volumes from a partner.
About Replica Volume Reserve
Each replicated volume has a replica volume reserve, which approximates the amount of in-use volume space. The value of the
replica volume reserve is used to allocate replica reserve for a volume.
When you congure a volume for replication, the primary group sets the initial value of the replica volume reserve:
• For volumes that are not thin-provisioned, 10 percent of the reported volume size. For example, if you have a 10GB volume that
is not thin-provisioned, the initial replica volume reserve is 1GB (10 percent of 10GB).
• For thin-provisioned volumes, the current volume reserve. For example, if you have a 10GB volume that is thin-provisioned with a
volume reserve of 2.5GB, the initial replica volume reserve is 2.5GB.
The initial value of the replica volume reserve appears in the Congure Replication – General Settings dialog box.
At the start of each replication operation, the primary group determines whether to increase the value of the replica volume reserve:
• For volumes that are not thin-provisioned, 10 percent of the reported volume size.
For example, if you have a 10GB volume that is not thin-provisioned, the initial replica volume reserve is 1GB (10 percent of
10GB).
• For thin-provisioned volumes, the current volume reserve.
For example, if you have a 10GB volume that is thin-provisioned with a volume reserve of 2.5GB, the initial replica volume reserve
is 2.5GB.
The size of the replica reserve for a volume is based on a percentage of the replica volume reserve. Therefore, as the replica volume
reserve increases, the replica reserve also increases, providing more space for replicas up to a limit.
About Backing Up and Protecting Your Data
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