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 68)
•
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
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.
CAUTION:
In the following cases, an operation of the reclaim zero pages stops and THP V-VOL
pages might be 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 while the operation to reclaim zero pages is in progress.
•
While the operation to reclaim zero pages is in progress, the initial copy operation of the
Continuous Access Synchronous pair, the Continuous Access Journal pair, the High Availability
pair, or the Business Copy pair is performed on the THP V-VOL.
Releasing pages in a THP V-VOL
The Storage Administrator (Provisioning) role is required to perform this task.
You can reclaim pages in a THP V-VOL to free pool capacity. If a page assigned to a THP V-VOL
contains only zero binary data, you can reclaim the page. The used capacity of the pool can then
be decreased. Before releasing pages in a THP V-VOL, see
“About releasing pages in a THP
).
To release pages in a THP V-VOL:
154 Configuring thin provisioning