Dell EqualLogic PS6210XS EqualLogic Group Manager Administrator s Guide PS Ser - Page 243

About Delegated Space and Replica Reserve, GroupB. See

Page 243 highlights

The local replication reserve size is based on a percentage (5 percent to 200 percent) of the volume reserve. For a thin-provisioned volume, the volume reserve size changes dynamically based on volume usage; therefore, the local replication reserve size also changes. The recommended local replication reserve percentage depends on whether you want to keep the failback snapshot: • No failback snapshot Specify 100 percent for the local replication reserve. • Keep the failback snapshot Specify 200 percent for the local replication reserve. Using the recommended values might not be the most efficient use of local replication reserve. Ideally, you want to allocate only enough space to meet the volume requirements. However, specifying too little space can prevent successful replication. The optimal value for local replication reserve depends on the volume change rate, the replication frequency, and whether you are keeping the failback snapshot. The volume change rate can be difficult to estimate. If you want to use less than the recommended value for local replication reserve, follow these guidelines: • No failback snapshot Size the local replication reserve based only on its use during replication. • Keep the failback snapshot Size the local replication reserve based on its use during replication and also for maintaining the failback snapshot. Then, combine the two values. About Delegated Space and Replica Reserve Replicas are stored in space that the secondary group delegates to the primary group. For example, if you want to replicate GroupA volumes and GroupB volumes to GroupC, GroupC must delegate space to GroupA and GroupB. See Figure 20. Delegated Space. Figure 20. Delegated Space About Backing Up and Protecting Your Data 243

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The local replication reserve size is based on a percentage (5 percent to 200 percent) of the volume reserve. For a thin-provisioned
volume, the volume reserve size changes dynamically based on volume usage; therefore, the local replication reserve size also
changes.
The recommended local replication reserve percentage depends on whether you want to keep the failback snapshot:
No failback snapshot
Specify 100 percent for the local replication reserve.
Keep the failback snapshot
Specify 200 percent for the local replication reserve.
Using the recommended values might not be the most
efficient
use of local replication reserve. Ideally, you want to allocate only
enough space to meet the volume requirements. However, specifying too little space can prevent successful replication.
The optimal value for local replication reserve depends on the volume change rate, the replication frequency, and whether you are
keeping the failback snapshot. The volume change rate can be
difficult
to estimate.
If you want to use
less
than the recommended value for local replication reserve, follow these guidelines:
No failback snapshot
Size the local replication reserve based only on its use during replication.
Keep the failback snapshot
Size the local replication reserve based on its use during replication and also for maintaining the failback snapshot. Then, combine
the two values.
About Delegated Space and Replica Reserve
Replicas are stored in space that the secondary group delegates to the primary group.
For example, if you want to replicate GroupA volumes and GroupB volumes to GroupC, GroupC must delegate space to GroupA and
GroupB. See
Figure 20. Delegated Space
.
Figure 20. Delegated Space
About Backing Up and Protecting Your Data
243