Thresholds – HP StorageWorks XP Remote Web Console Software User Manual
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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”
). 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.
To set the pool capacity to a sufficient level when the hosts write to the V-VOL, call HP Technical
Support. You can make such settings if the pool is not associated with V-VOLs exceeding the pool
capacity. If the total V-VOL capacity exceeds the pool capacity after you perform such settings,
you cannot associate V-VOLs with the pool or increase the V-VOL capacity.
Once capacity has been added to the pool then the administrator should use the Remote Web
Console Data Retention window to view the V-VOLs impacted by the previous pool-full condition
and also to reset the protection status of the V-VOL. Once the protection status is reset, normal
operations can be returned to the hosts.
Thresholds
XP Thin Provisioning monitors V-VOLs capacity and pools capacity by thresholds. There are two
types of thresholds: V-VOL thresholds and pool thresholds.
•
Pool thresholds: A pool threshold is the proportion (%) of used capacity of the pool to the total
pool capacity. Each pool has its own Pool threshold values that are divided into a variable
threshold and a fixed threshold, for example:
◦
Threshold 1: You can set it between 5% and 95%, in 5% increments. The default value
is 70%.
◦
Threshold 2: Fixed at 80%.
Pool usage over either threshold will cause a warning to be issued via a SIM and an SNMP
trap.
Example: When the total pool capacity is 1 TB and threshold 1 is 50%
shows the pool capacity (when pool threshold 1 is 50%). If the used
capacity of the pool is larger than 50% (500 GB) of the total pool capacity, a SIM and an
Managing Pool Capacity
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