IBM DS8900F, Введение и руководство по планированию

Страница: 51 / 172

Count key data and fixed block volume deletion prevention
By default, DS8000 attempts to prevent volumes that are online and in use from being deleted. The DS
CLI and DS Storage Manager provides an option to force the deletion of count key data (CKD) and fixed
block (FB) volumes that are in use.
For CKD volumes, in use means that the volumes are participating in a Copy Services relationship or are in
a path group. For FB volumes, in use means that the volumes are participating in a Copy Services
relationship or there is I/O access to the volume in the last five minutes. With Safeguarded Copy, in use
means that the volumes have data saved in the backup repository.
If you specify the -safe option when you delete an FB volume, the system determines whether the
volumes are assigned to non-default volume groups. If the volumes are assigned to a non-default (user-
defined) volume group, the volumes are not deleted.
If you specify the -force option when you delete a volume, the storage system deletes volumes
regardless of whether the volumes are in use. However, an in use volume that has Safeguarded Copy
space cannot be deleted with the -force option.
Thin provisioning
Thin provisioning defines logical volume sizes that are larger than the usable capacity installed on the
system. The volume allocates capacity on an as-needed basis as a result of host-write actions.
The thin provisioning feature enables the creation of extent space efficient logical volumes. Extent space
efficient volumes are supported for FB and CKD volumes and are supported for all Copy Services
functionality, including FlashCopy targets where they provide a space efficient FlashCopy capability.
Releasing space on CKD volumes that use thin provisioning
On an IBM Z host, the DFSMSdss SPACEREL utility can release space from thin provisioned CKD
volumes that are used by either Global Copy or Global Mirror.
For Global Copy, space is released on the primary and secondary copies. If the secondary copy is the
primary copy of another Global Copy relationship, space is also released on secondary copies of that
relationship.
For Global Mirror, space is released on the primary copy after a new consistency group is formed.
Space is released on the secondary copy after the next consistency group is formed and a FlashCopy
commit is performed. If the secondary copy is the primary copy of another Global Mirror relationship,
space is also released on secondary copies of that relationship.
Extent Space Efficient (ESE) capacity controls for thin provisioning
Use of thin provisioning can affect the amount of storage capacity that you choose to order. ESE capacity
controls allow you to allocate storage appropriately.
With the mixture of thin-provisioned (ESE) and fully-provisioned (non-ESE) volumes in an extent pool, a
method is needed to dedicate some of the extent-pool storage capacity for ESE user data usage, as well
as limit the ESE user data usage within the extent pool. Another thing that is needed is the ability to
detect when the available storage space within the extent pool for ESE volumes is running out of space.
Thin-provisioning capacity controls provide extent pool attributes to limit the maximum extent pool
storage available for ESE user data usage, and to guarantee a proportion of the extent pool storage to be
available for ESE user data usage.
An SNMP trap that is associated with the thin-provisioning capacity controls notifies you when the ESE
extent usage in the pool exceeds an ESE extent threshold set by you. You are also notified when the
extent pool is out of storage available for ESE user data usage.
Thin-provisioning capacity controls include the following attributes:
Chapter 3. Data management features 37