VMAX All Flash compression feature – released with HYPERMAX OS 5977.945.890
Some key points:
1. This new feature compresses data before it is written to flash drives.
2. Compression is managed per Storage Group level.
3. Approx 2:1 savings in storage efficiency.
4. One compression I/O module is required per director, which are installed on all VMAX All Flash systems.
How to quickly check if compression is enabled OOTB on a VMAX All Flash Array?
This question arose recently,thanks to @rawstorage for pointing me in the right direction.
You may either simply run the following symcfg command or lookup Unisphere as follows:
symcfg list -srp -v

From Unisphere navigate to Storage->Storage Groups Dashboard->SRP_1:

From Symmwin you can view the compression ratio that was set by clicking on the SRP tab and checking the FBA Compression field, from the image below you can see the value set is 2.00 which implies the Compression ratio is set to 2:1 :

Note: The system must have been sized to accommodate upgrading to and enabling compression.
Vblock/VxBlock 740
It is best practice to disable compression on Storage Groups containing boot LUNs, these would be boot LUNs assigned to Cisco UCS blades which boot from SAN.
Useful Links in relation to VMAX All Flash compression:
VMAX All Flash & Compression (Video)
VMAX ALL FLASH WITH THE ADAPTIVE COMPRESSION ENGINE
5977 2016 Q3 SR – Compression, SRDF/Metro et al
Using EMC VMAX Storage in VMware vSphere Environments (Chapter3)