Adding MDisks to storage pools using the CLI
You can use the command-line interface (CLI) to add managed disks (MDisks) to storage pools.
Before you begin
The MDisks must be in unmanaged mode. Disks that already
belong to a storage pool cannot
be added to another storage pool until
they have been deleted from their current storage pool. An MDisk can
be deleted from a storage pool under these circumstances:
- If the MDisk does not contain any extents in use by a volume
- If you can first migrate the extents in use onto other free extents within the group
About this task
Important: Do not add an MDisk using this procedure
if you are mapping the MDisk to an image mode volume. Adding an MDisk
to a storage pool enables the Storwize® V3700 to
write new data to the MDisk; therefore, any existing data on the MDisk
is lost. If you want to create an image mode volume, use the mkvdisk command
instead of addmdisk.
If you are using a Storwize V3700 flash drive managed disk, ensure that you are familiar with the flash drive configuration rules.
The Storwize V3700 performs
tests on the MDisks in the list before the MDisks are allowed to become
part of a storage pool when:
- Adding MDisks to a storage pool using the addmdisk command
- Creating a storage pool using the mkmdiskgrp -mdisk command
These tests include checks of the MDisk identity, capacity, status and the ability to perform both read and write operations. If these tests fail or exceed the time allowed, the MDisks are not added to the group. However, with the mkmdiskgrp -mdisk command, the storage pool is still created even if the tests fail, but it does not contain any MDisks. If tests fail, confirm that the MDisks are in the correct state and that they have been correctly discovered.
These events
contribute to an MDisk test failure:
- The MDisk is not visible to all Storwize V3700 nodes in the clustered system.
- The MDisk identity has changed from a previous discovery operation.
- The MDisk cannot perform read or write operations.
- The status of the MDisk can be either degraded paths, degraded ports, excluded, or offline.
- The MDisk does not exist.
These events contribute to an MDisk test timeout:
- The disk controller system on which the MDisk resides is failing.
- A SAN fabric or cable fault condition exists that is preventing reliable communication with the MDisk.
Note: The first time that you add a new flash drive to a pool, the flash drive is automatically formatted and set
to a block size of 512 bytes.
Procedure
To add MDisks to storage pools, complete the following steps.