Release Notes

26 Dell PS Series: Space Borrowing for Snapshots and Replicas | TR1084 | version 2
5.1.4 Space borrowing with low total replica reserve (replication)
Even with plenty of delegated space and borrowable space, if there is insufficient replica reserve on the secondary
group, the system will require manual administrative intervention to increase the amount of total replica reserve
space to complete an active replication operation.
In this example, a new 100 GB thick volume on the primary group is configured for replication with the minimum total
replica reserve, 105%. This means that 100% is dedicated to the current replica volume reserve, and 5% is reserved for
additional replicas in the total replica reserve.
When replication is enabled on this volume, a 100 GB thin-provisioned replica volume will be created on the secondary
group, even though the primary volume is thick. This is typical behavior when enabling volume replication. As the 100
GB replica volume is thin provisioned, 10% of the replica volume will be reserved by default for thin provisioning. This
yields a 10 GB current replica volume reserve (10% of 100 GB).
Total replica reserve is a percentage of current replica volume reserve. As the total replica reserve is 105%, and the
current replica volume reserve is 10 GB, 105% of 10 GB results in a 10.5 GB total replica reserve. 100% of the 10 GB
(10GB) are in use in the current replica volume reserve, and a remaining 5% of the 10 GB (0.5 GB) is available for
additional replicas in the total replica reserve.