How to safely remove a disk group from a storage pool?

[nkrivtsov]

Hello! We have MSA 2060 with Advanced Data Services E‑LTU.

In disk pool A, we have 12 SSD disks and 24 HDD disks with tiering.

We want to move slow HDD disks to Pool B.

Is it possible to remove slow HDD disks from Pool A without data loss?

Thanks!

[Moderator edit: Removed the confidential info]

[JonPaul · Accepted solution]

@nkrivtsov 
Virtual storage will take care of moving the data from the HDD disk-group to the SSD disk-group.  This can take a long time but if I read your configuration correctly, only about 2TB of data is on disk-group dgA02.  There is enough space available on dgA01 to 'land' that data.
VDRAIN is the feature you are looking for, that happens automatically when you remove a disk-group from a Pool.
There is information and caution in the MSA 2060 Storage Management Guide:  https://support.hpe.com/hpesc/public/docDisplay?docId=a00128580en_us&docLocale=en_US

And a blurb in the Virtual Storage Technical Guide:  https://www.hpe.com/psnow/doc/a00103247enw
Search guides for 'drain'

You can also monitor VDRAIN process by looking at the tier-statistics in the CLI
CLI>  show tier-statistics tier all
This will show pages allocated and deallocated per tier
or
CLI>  show disk-group-statistics
This will show pages allocated and deallocated per disk-group

[nkrivtsov]

Hello!

Thanks for your help, it was helpful for me.

[Sunitha_Mod]

Hello @nkrivtsov,

That's excellent! 

We are extremely glad to know your concern has been addressed.