Home > Storage > PowerMax and VMAX > Data Protection > Dell PowerMax 2500 and 8500: TimeFinder SnapVX Snapshots and Clones > Storage resource pool considerations
Snapshot deltas are always stored in the storage resource pool (SRP) where the source volume resides. Linked targets and clones in the same SRP as the source are space-efficient, pointer-based copies. Data only copies to linked targets and clones that do not reside in the same SRP as the source.
If the source volumes and linked targets or clones are in separate SRPs, the target SRP must be configured to support the targets’ capacity and performance requirements. The target state is reported as copied when the background process has completed.
Best practice: Single SRP systems are the recommended best practice for simplified management and performance benefits of spreading workloads across all resources in the array. Rather the separating local array resources to protect against internal hardware failures, use SRDF remote replication for a higher level of protection external to the array.
The Reserved Capacity setting allows the user to limit the amount of storage in the SRP that the replicas can consume. There is no need to physically separate production volumes and their replicas.
Reserved Capacity is a percentage SRP capacity that is only available to new host writes. Existing and new snapshots are affected if the Free Capacity of the SRP falls below the set Reserved Capacity. For example, if the reserved capacity on an SRP is set to 10% and the SRP becomes 90% full, only new host writes can consume the available capacity.
When only Reserved Capacity is available in an SRP, new snapshots cannot be created, and existing standard snapshots fail at the next attempt to create a snapshot delta. Failed snapshots need to be terminated manually. Existing secure snaps do not fail when Reserved Capacity is reached, but new secure snaps cannot be created.
The Storage Resource Pools page displays the Reserved Capacity setting and snapshot capacity usage of the selected SRP. The Reserved Capacity setting can be changed by selecting Modify.
Note: The Reserved Capacity value also applies to SRDF/A delta set extension data.
Best practice: Lowering the Reserved Capacity setting is acceptable if the additional free capacity is sufficient for the required snapshots. However, be sure to assess the overall situation to determine if any other action is required such as adjusting snapshot schedules or deleting unneeded snapshots or volumes. If the application needs the specified recovery points and schedules or retention cannot be adjusted, consider increasing capacity on the array.
The snapshot SRP utilization alert triggers on preset threshold values for a percentage of SRP capacity used by snapshot data. Custom alerts can also be created with customized thresholds for specified Storage Groups in Unisphere.