Types (Components); Dynamic Capacity Management; Dynamic Capacity Management Overview - HP 418800-B21 - StorageWorks Modular Smart Array 70 Storage Enclosure User Manual

Snapshot
lifetime
Short
Long
Demand-allocated snapshots
When a snapshot is demand allocated, the storage system allocates only enough space to store metadata
and pointers to the source data. As the source is overwritten, the array allocates more space and copies
the original data to the snapshot. If all the original data on the source is over-written, the controller
increases the allocated space on the snapshot to the full size of the source.
The size of the disk group in which the source and snapshot are located must be sufficient to handle
increases in snapshot size, whenever the increases might occur. Insufficient space in the disk group can
not only prevent the controller from increasing the space allocation, but it can also prevent writes to
both the source and snapshot.
Fully allocated snapshots
When a snapshot is fully allocated, the storage system allocates only enough space to store metadata
and pointers to the source data, but reserves space equal to the capacity of the source virtual disk. As the
source is overwritten, the array allocates more space and copies the original data to the snapshot.
Once created, a fully allocated snapshot cannot run out of space.

Types (components)

The type property indicates the component structure of the host volume. This varies with the host operating
system and logical volume manager. Examples:
Device. All OSs.
Logical volume. AIX, HP-UX, Linux, Solaris, Tru64 UNIX
Partition (slice). AIX, HP-UX, Linux, Solaris, Windows. See
Volume set, dynamic disk, spanned volume. Windows

Dynamic capacity management

Dynamic capacity management overview

DC-Management provides you with the capability to extend (increase) or shrink (decrease) the size of a
host volume without disrupting host I/O. This gives you greater control over the size of host volumes as
your system storage requirements change.
If a host volume is nearing capacity, you can extend the size of the volume to avoid the situation that
occurs when a host volume reaches its full capacity. If a host volume has too much capacity allocated to
it, you can shrink the size of the volume, freeing up the unused capacity for other applications.
DC-Management can be implemented manually or automatically.
• Manual DC-Management enables you to immediately change the volume size. The new size
remains in effect until you manually reset it again.
• Automatic DC-Management policies enable you to specify the threshold at which you want
the size of the volume to be changed. RSM monitors the capacity of the host volume and
automatically changes the size when the specified threshold is reached. You can set e-mail
notification alerting you when a volume has been resized. You can also control the time during
which the policy is enforced.
152
Host volumes
Estimated changes
in source data
Less than 25%
25% or more
Recommended
snapshot type
Demand allocated
Fully allocated
partitions and slices.