PREALLOCREDUCTIONRATE

The PREALLOCREDUCTIONRATE option specifies that the server reserves less physical space than is normally allocated in directory-container and cloud-container storage pools for backup and archive operations from client nodes. The option can also be used to reserve less space on target replication servers for replication operations. It can be useful to allocate less space in cases when the volume of incoming data will be reduced by data deduplication and compression operations.

If the PREALLOCREDUCTIONRATE option is not set, the default behavior is that the server allocates space for pre-deduplicated and compressed data in the directory-container and cloud-container storage pool directories. With a smaller cloud accelerator cache (storage pool directories that are defined to the cloud-container storage pool) and set workloads, for example, large database backups, an operation might exceed the capacity of the accelerator cache and the backup might fail.

Although the PREALLOCREDUCTIONRATE option applies to directory-container and cloud-container storage pools, the option can be especially beneficial in certain scenarios with cloud-container storage pools. For example, if you want to configure a smaller cloud-container storage pool cache and the data reduction ratios are certain, use the option. If you are backing up data to cloud-container storage pools, ensure that you verify the cloud cache capacity. If the cache still has inadequate space even after data reduction, backup failures can occur.

Syntax

Parameters

data_reduction_ratio: Specifies the assumed ratio of data reduction for data that is ingested to a directory-container or cloud-container storage pool. The default is 1. The minimum value is 1 (no reduction). The maximum value is 25 (a 25:1 assumed reduction).

Example 1

Specify an assumed data reduction ratio of 5:1 when data is transferred from the front end to the back end. With this reduction ratio, only one unit of back-end space is reserved per 5 units of protected front-end data.

preallocationreductionrate 5

Example 2

By default, the server preallocates space for the entire front end (in a typical scenario, tens of terabytes). On the back end, hundreds of terabytes of object storage are available for the cloud-container storage pool, so the customer, Lisa, did not expect the backup operation to fail. Lisa discovers that not enough space is available in the accelerator cache and that there should be at least 5 TB of capacity in the accelerator cache. She also has recent data to show that a 50 TB backup is reduced to 5 TB (10:1 data reduction). Lisa expresses confidence in her numbers and opts to use the PREALLOCREDUCTIONRATE option to help ensure successful backup operations.

preallocationreductionrate 10