Administrator Guide

virtual volume will inherit the thin capabilities of the target device. Migrating thin-capable storage provides you more information
on the thin-capable storage migrations.
The following table describes how metro node supports the thin-aware functionalities (based on the understanding of metro
node whether the arrays are thin capable).
Table 4. Array thin capability during migration
Functionality Thin-capable arrays Arrays that are not thin-capable
Thin provisioning
● Discovers the thin volumes on the backend
● Automatically sets the thin-rebuild flag as
part of the storage volume claiming process
● Supports the provisioning of thin volumes on the
array through VIAS provisioning
● Creates the thin-enabled virtual volumes
● Supports the manual tagging of the thin
volumes with the thin-rebuild flag
as part of the storage volume claiming
process
Thin storage
management
● Supports the SCSI UNMAP command from the
host
● Support out-of-space notifications to the host
from the last leg that services I/O
Not supported
Thin rebuild
● Automatically sets the thin-rebuild flag as
part of the storage volume claiming process
● Uses the SCSI UNMAP command to free up the
storage blocks on the out-of-date leg
● Supports the manual tagging of the thin
volumes with the thin-rebuild flag
as part of the storage volume claiming
process
● Uses zero writes as part of the mirror
synchronization for the unused blocks
Thin migration
● Retains thin storage management capabilities
of virtual volume only when migration happens
between thin-capable volumes of same storage-
array family.
● In other scenarios, virtual volume loses thin
storage management capabilities during migration,
and restores them when migration is committed.
Normal migration behavior with optimization
for the unused area.
Thin provisioning
In metro node, thin provisioning is performed through the legacy method (using the EZ provisioning or the Advanced
provisioning methods) and through VIAS.
Thin provisioning provides you more information on these methods.
Creating thin-enabled virtual volumes
Metro node supports creating virtual volumes that exhibit thin capabilities to the hosts. To exhibit these capabilities, certain
requirements have to be met. The requirements are as follows:
● Storage volumes are provisioned from storage arrays that are supported by metro node as thin-capable (where the thin
properties are shown). The storage volumes must also be from a storage-array family that metro node supports (Dell EMC
PowerStore, Dell EMC UnityXT). The value corresponding to the storage-array-family property must be XTREMIO,
CLARiiON, or SYMMETRIX and it must not be other or -.
● Storage volume display thin properties.
● All the mirrors are created from the same storage-array family that metro node supports (For a RAID-1 configuration).
The value corresponding to the storage-array-family property must not be mixed, other or -. In the following
scenarios, the thin capable attribute can show false even if the mirrors are created from the same storage-array
family that metro node supports:
○ The array software does not support the UNMAP feature
○ The UNMAP feature is not turned on the arrays
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Thin support in metro node