HP XP Racks - Manual (Page 152)

5. Click Finish.
6. In the Confirm window, confirm the settings, in Task Name type a unique name for this task
or accept the default, and then click Apply.
If Go to tasks window for status is checked, the Tasks window opens.
About releasing pages in a THP V-VOL
Releasing pages in a THP V-VOL frees up pool capacity. When a page in the THP V-VOL contains
zero data, the free capacity of a pool increases after the pages are released. You can perform
the operation to reclaim zero pages on each V-VOL and monitor progress. For details, see
“View
Pool Management Status window” (page 375) . If you stop the operation to reclaim zero pages, the
zero pages that have been reclaimed cannot be restored.
Logically, there is no difference between a page with just zero data and the area of a THP V-VOL
without a page allotted. Both are effectively identical. However, the former uses pool capacity and
the latter does not.
Zero pages can be reclaimed when all the following conditions are satisfied:
•
The THP V-VOL is not used in conjunction with another HP XP7 Storage product which does
not support reclaiming zero pages.
See “Using Thin Provisioning or Smart Tiers with other HP XP7 Storage products” (page 67) .
•
LDEV formatting is not being performed on the THP V-VOL.
•
The THP V-VOL is not blocked.
•
The THP V-VOL is associated with a pool.
•
The pool associated with the THP V-VOL is not blocked, or is full and blocked.
Pages that include control cylinders are not processed when releasing pages in a THP V-VOL.
Pages that include file system metadata cannot be reclaimed. Refer to “Operating system and file
system capacity” (page 65) for a table of the Pool Capacity Consumed by the file system.
While releasing pages from a THP V-VOL, performance of the host I/O to the THP V-VOL may
temporarily decrease due to scanning for non-zero data.
If you stop an operation to reclaim zero pages in mid-stream, the pages that have been released
will remain as free pool capacity.
After an operation to reclaim zero pages, Thin Provisioning automatically balances usage levels
among parity groups in the pool. This rebalancing is performed on parity groups related to the
pool. If you do not want automatic balancing of the usage levels of parity groups, call HP Technical
Support to change your configuration.
Thin Provisioning does not automatically balance the usage levels among parity groups if the cache
memory is not redundant or if the pool usage reaches up to the threshold.
If all the tracks that belong to a page assigned to a THP V-VOL have no records written, you can
reclaim the page and return it to the pool's available capacity.
In the following cases, an operation reclaim zero pages stops and THP V-VOL pages are not
released.
•
The pool-VOL accessed by the target THP V-VOL is blocked.
•
The pool associated with the target THP V-VOL is blocked while the operation to reclaim zero
pages is in progress.
•
Cache memory failure occurs the operation to reclaim zero pages is in progress.
•
The initial copy operation between Continuous Access Synchronous pair, Continuous Access
Journal, Business Copy pair is performed on the THP V-VOL in which the zero pages are
reclaimed.
152 Configuring thin provisioning