VMAX AFA – Compression Notes

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)

Posted on December 23, 2016 5 By David Ring Storage Posted in Storage, Uncategorized Tagged #AFA, Compression, VMAX ALL FLASH

David Ring

5 Comments »

Jim Williams
January 31, 2019 at 8:41 pm Reply

Hi,

VMAX AFA 950Fx. I have a customer that wants to place a device (lun) in multiple storage groups. I received the error “cannot have a lun in multiple storage groups under FAST control”. I found out that if you remove or un-associate the lun from the SRP (none) you can add the device to another SG. I see compression gets disabled on the lun after removing is from the SRP. Any thoughts on this pro, con don’t do it etc?

Customer want to know how to handle this situation. I assume they do not want to keep the lun in multiple SGs all the time. But they are asking me how to handle this and a work-around from getting the FAST error.

Any caveats etc?

Thanks
- David Ring
  January 31, 2019 at 10:45 pm Reply
  
  Hi Jim, This is a FAST limitation when manipulating devices in Storage Groups. A Symmetrix device may only belong to one storage group under FAST control.
  - Jim Williams
    January 31, 2019 at 11:11 pm
    
    Thanks for the reply. I’m just curious how the lun and or SG is impacted when you remove it from the SRP and compression gets grayed out etc. I assume this would only be required for a short time… but if someone forgot about it and left if that state etc. hummm….
    
    I wouldn’t think the luns would get uncompressed etc. And I assume compression is disabled in that state since it is grayed out. I also wonder if SRDF/A would be impacted by this for those luns…
Man Cristian
February 25, 2019 at 12:22 pm Reply

It is possible to put a device in multiple storage groups. but you have to create a new SG witn no -SLO and -SRP option. Then will work. I have those kind of configuration (same LUN;s in different MV’s/SG’s).
- Jim Williams
  March 1, 2019 at 5:59 pm Reply
  
  I stumbled across doing that. But my understanding is compression gets disabled in doing so.
  
  Thanks

DavidRing.ie