I have a VMAX3 All Flash too and interested to know about performance impact by turning this feature on.

We have multiple all flash arrays and it is a requirement to turn on the compression for any and all new additions to the array.

Someone else on DECN will need to chime in to provide further validation. We meaning our storage team turn SLO on for all, and on AFA's we do enable compression. 

SLO=Service Level Offering

sudo symsg -sid 617 -sg set -srp SRP_1 -slo Optimized

AFA=All Flash Array  SLO=Service Level Offering

symsg -sid 617 -sg set -srp SRP_1 -slo Diamond -compression

You won't see good compression until the storage actually starts to get data on it. Then you will see the ratio rise.

EMCs innovation in these particular arrays is that the Compression component is a separate Adaptive Compression Engine in itself to be precise it is 1 per director.

There are 4 main components in the AFA one of which is the Adaptive Activity based compression on a Hardware Acceleration card included in the AFAs.

Basically this particular IO module in the AFAs offloads the workload from the CPU and other resources having no impact of the compression workload.

So i think there wont be any impact on Vmware if you enable the compression.

Regarding the time it takes, i do really know much about it.

Hope this helps