Volume and Diskgroup relationship?

[Seantom]

Hello,I have MSA 2040 with 24 total 600G drives,

we would like to upgrade 10 of the drives with 2.4 TB

drives are:  HPE MSA Q2R41A 2.4TB 10kRPM 2.5in SAS-12G Enterprise HDD

The first step is to clear the disk-group/Volume and then delete or migrate to another volume. However we are unable to map volume to Disk group. Please help.  is there any command that can show what diskgroup are under each volume

[ArunKKR]

Hi,

MSA 2040 supports both linear disk group configuration and virtual pools configuration.
Volumes fall directly under disk group in linear disk group configuration.
I believe that your current configuration uses virtual pools.

You may execute the below commands to confirm the same:

show pools
show disk-groups

In virtual pool, volumes do not fall directly under disk group.
They come under the virtual pool A or Pool B.
Data in volumes is spread across disk groups in a Virtual pool.

Please refer to the below advisory for information on vdrain process involved when a disk group in a pool is deleted.

https://support.hpe.com/hpesc/public/docDisplay?docId=a00018177en_us&docLocale=en_US

From the advisory:

For HPE MSA 2040/1040 and HPE MSA 2050 SAN arrays, when a disk group is removed from a pool, any data in that disk group will need to be drained to the remaining disk groups within the same pool. This process is known as a VDRAIN process. Depending on the amount of data in the disk group, the VDRAIN process may take a few hours or a much longer period of time to complete. If a user wishes to re-create disk group allocation on a pool quickly, using the VDRAIN utility may not be the best available course of action to take.

For a faster alternative to the VDRAIN utility, the current pool data should be carefully backed up and verified as valid. Delete the pool using the following CLI command:

CLI# delete pools A|B

Once the old pool has been deleted, re-create the new pools with the disk group layout and capacity required. Data can then be restored to the new disk groups immediately, and accessed.

Please elaborate on your query and configuration based on the above feedback.

[ArunKKR]

Hi,

Please let us know whether the information shared addressed your query.

[Seantom]

Thank you so much for info.

So this is what i got after reading all documentations etc.

1. Disk group is bunch of disk in any given raid format.

2. DiskGroup are part of either Pool A or Pool B

3. Volume is created from Pool A or Pool B.  Each disk has no direct relationship to Volume. In other words if i delte a diskgroup it should auto drain data and copy to other drives that are part of the pool. Since i have total of 38TB and about 18TB avaialble so i should be ok to delte diskgroup of 2TB and add new HDD drive, Create new diskgroup and add to the Pool i removed the drives.

4. Also by going to performance i should be able to see how much disk disk space disk is using.

[ArunKKR]

Hi,

The first 2 points seems to be correct.

Disk group vdrain is a slow process and cannot be interrupted once its initiated.

If there are 2 disk groups in a Pool when one of the disk groups is deleted all the data in the disk group will be moved to the other disk group (provided the working disk group has enough free space to accomodate the data in the disk group that is being deleted)

The amount of data occupied by each disk should not matter. 

Its the free space in each disk group that decides whether we can delete a disk group.

Please share the output of the below commands so that I could provide a better answer:

show pools

show disk-groups

show volumes

You may delete the serial number information from the command outputs.