HP StorageWorks XP Remote Web Console Software - Manual (Page 14)

Figure 4 Managing Usage Rates and I/Os
Full Pool Handling
Full Pool conditions can be managed in two ways. The difference between the two handling
methods is how a V-VOL is treated if it requires new pool capacity when no capacity is available.
The default method used during a full pool condition is to fail some read and write operations to
V-VOLs using the pool. Read and write operations are handled in the following way:
•
Successfully read data that already exists in the V-VOL. Reads to Pool Pages already assigned
to the V-VOL are successful.
•
Successfully update (write) data that already exists in the V-VOL. Writes to Pool Pages already
assigned to the V-VOL are successful.
•
Fail a read operation that specifies an LBA address that is not assigned to a page. This read
would be for an area that has never been written to the V-VOL.
•
Fail a write operation that species an LBA address that is not assigned to a page. This write
operation requires free pool capacity that is not available.
The second method used during a full pool condition is enabled using System Option Mode 729.
Call HP Technical Support to inquire how to enable this option (see
“Calling HP Technical Support”
(page 86) ). This method uses Data Retention Utility to manage V-VOLs that are impacted by the
pool full condition. Only V-VOLs that have required free pool capacity during a pool full condition
are impacted. All V-VOLs that have not requested free capacity continue to operate without any
read or write problems imposed by the pool full condition.
Using the second method, a V-VOL that requests a free page from the pool to support a write to
an LBA address that is not mapped to an existing allocated page to the V-VOL is immediately
changed to Protect status using Data Retention Utility. In this case, the V-VOL becomes read and
write protected when a write fails due to the pool-full condition. This protection status preserves
the integrity of the V-VOL by making it inaccessible.
If a V-VOL is set to Protect status, the Remote Web Console Data Retention window indicates that
the Protection attribute was added to the V-VOL, the S-VOL column displays Enable, and the
Retention Term column displays 0 days. However, if the Protect attribute is added to a V-VOL with
the S-VOL Disable attribute, the S-VOL column remains Disable.
14 About XP Thin Provisioning Operations