Reducing ASM disk size (Azure)

Oracle requires that all disks in an ASM disk group should be of the same size (link). Therefore, in-place resize is not possible and the procedure below should be followed instead.

1. Create and attach new disks of the desired size to the database node VMs. Attach the disks using LUN numbers 1 through 49 - these LUNs will be shared automatically by FlashGrid Storage Fabric.

   Note: Read-only caching must be enabled for all new disks. Read-Write and None modes are not supported and may create reliability problems.

   Note: It is recommended to enable Performance Plus for all new disks. Performance Plus is mandatory if existing disks in the disk group already have it enabled.

   Note: to create Premium SSD v2 disks, use this article.

2. Confirm FlashGrid names of the new drives, e.g. rac2.lun3

   $ flashgrid-cluster drives

   If the new drives are not listed then check that the corresponding devices (e.g. /dev/lun3) are visible in the OS. If they are visible in the OS then run as root flashgrid-node reload-config and check output of flashgrid-cluster drives again. If they are not visible in the OS then double-check that you have attached them with correct LUN numbers.

3. Run the following command to replace all regular (non-quorum) disks in a disk group:
   

   $ flashgrid-dg replace-all-disks -G <diskgroup_name> -d <disk> [<disk> ...]

   For example, to replace all regular disks in the DATA disk group with lun5, lun6:

   $ flashgrid-dg replace-all-disks -G DATA -d /dev/flashgrid/rac[12].lun[56]

   This command relocates data from the old disks to the new ones and runs rebalance. It can generate significant I/O load, so plan it during time when the database is less active.
   Note: Starting with Storage Fabric version 23.04, the replace-all-disks operation executes data rebalance in background. While rebalance is running in background, the flashgrid-cluster and flashgrid-dg commands may show old disks reported as "LostDisks". This will be cleared after the background operation completes.
4. The old disks can be removed. Please run for each DB node:

   [fg@<db_node> ~] flashgrid-node stop-target <disk>

   For example, to stop disk rac1.lun3 on rac1, run:

   [fg@rac1 ~] flashgrid-node stop-target /dev/flashgrid/rac1.lun3

   To stop disk rac2.lun3 on rac2, run:

   [fg@rac2 ~] flashgrid-node stop-target /dev/flashgrid/rac2.lun3

5. Detach the old disks from the VMs.