IBM Storwize V7000 Unified Problem Determination Manual page 324

Allocate storage from available external storage: The system supports adding
external storage systems to provide additional capacity and virtualization. If your
environment has external storage systems, you can increase capacity to the storage
pool by completing these steps:
1. In the management GUI, select Pools > External Storage.
2. Select the storage system to view a list of MDisks that are currently detected on
3. Right-click an unmanaged MDisk and select Add to Pool.
4. On the Add to Pool dialog, select the pool and click Add to Pool.
5. Verify that the MDisk was added to the selected pool by expanding the pool
Decreasing the size of the file system
If adding more capacity to the storage pool is not possible, you can also decrease
the size of the file system by removing network shared disks (NSDs) that provide
volume capacity to the compressed file system. Use this method if the file system
is still online and there is enough capacity on the physical storage.
A compressed file system is comprised of five compressed NSDs, which averages
to about 70% of the capacity. This capacity is then allocated to the file system and
is compressed in the storage pool. Removing the NSD deletes the compressed
volume and triggers data migration to the other NSDs that make up the
compressed file system. As data is migrated to the remaining NSDs, overall file
system capacity is reduced while keeping the storage capacity the same, thus
making the overestimated compression ratio more easily managed. Actually the
storage capacity could shrink as well if files had previously been deleted. The
redistribution of data to other volumes by removing an NSD will not redistribute
deleted files, and also may place data on blocks where deleted files had been
placed.
Before removing the NSD, ensure that the following prerequisites are met:
v Ensure that the file system has enough capacity to shrink.
v Ensure that there is temporary spare capacity within the block storage pool.
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Storwize V7000 Unified: Problem Determination Guide Version
the external storage system. If there are no MDisks that are displayed, click
Detect MDisks. If theStorwize V7000 Unified system attached to external
storage systems, you can allocate additional LUNs.
and ensuring that the added MDisk is displayed.
While data is migrated, all the data on the NSD that is being deleted exists on
the storage pool twice. To ensure that the migration does not fail due to lack of
space, check that the storage pool has enough free capacity to store the
compressed volume data that is being migrated. To determine whether the free
capacity on the storage pool is sufficient for the compressed volume data being
migrated, complete these steps:
1. In the management GUI, select Files > File Systems and ensure that the NSD
view is selected.
2. Expand the compressed file system and its associated storage pool and
right-click the NSD that you plan to delete.
3. Select Properties.
4. On the Properties panel, ensure that Show Details is selected.
5. On the right side of the panel, under the Capacity heading, the real capacity
for the compressed volume is displayed. The storage pool must have at least
the real capacity of the volume to successfully migrate the data.