Symptoms
Data reduction ratio is low, and many devices are uncompressed.
Cause
As designed, compression is enabled on storage groups, not on individual devices.
If the thin devices are not assigned to a storage group, they will stay uncompressed. If there are many uncompressed devices, this will result in a low DRR.
Resolution
Assign these TDEVS into storage groups which have compression enabled on them.
Run this command to check if the TDEVs are not assigned to a storage group:
symcfg list -sid <XXX> –sg_compression
Run this command to check if storage groups have compression enabled on them:
symsg -sid <XXX> list
Compression is enabled on SGs by default; however, these settings can be changed.
Affected Products
PowerMax, PowerMaxOS 5978