Planning for compression in pre-existing installations
To use compressed volumes without affecting performance of existing non-compressed volumes in a pre-existing system, ensure that you understand the way that resources are reallocated when the first compressed volume is created.
Compression requires dedicated hardware resources within the node canisters which are assigned or de-assigned when compression is enabled or disabled. Compression is enabled whenever the first compressed volume in an I/O group is created and is disabled when the last compressed volume is removed from the I/O group.
As a result of the reduced hardware resources available to process non-compressed host-to-disk I/O, you should not create compressed volumes if the CPU utilization of node canisters in an I/O group is consistently above certain values. Performance might be degraded for existing non-compressed volumes in the I/O group if compressed volumes are created.
Use in the management GUI during periods of high host workload to measure CPU utilization.
If your system currently does not use compression, the system automatically analyzes your configuration to determine the potential storage savings if compression is used. The management GUI incorporates the Comprestimator utility that uses mathematical and statistical algorithms to create potential compression savings for the system. The analysis for potential savings can be used to determine whether purchasing a compression license for the system is necessary to reduce cost of extra storage devices. To estimate compression savings in the management GUI, select .
After the analysis completes, you can download a savings report that shows estimated savings for all the volumes with enough data to be analyzed. This report lists all currently configured volumes on the system and their potential compressions savings. To download a report, select .