HP XP Racks - Manual (Page 139)

Thresholds
Pool utilization thresholds
Thin Provisioning monitors pool capacity using thresholds. A threshold is the proportion (%) of used
capacity of the pool to the total pool capacity. Each pool has its own pool threshold values.
•
Warning Threshold: Set the value between 1% and 100%, in 1% increments. The default is
70%.
•
Depletion Threshold: Set the value between 1% and 100%, in 1% increments. The default is
80%. The depletion threshold must be higher than the Warning threshold
Pool usage over either threshold will cause a warning to be issued in the form of SIMs (Service
Information Messages) to Remote Web Console and SNMP (Simple Network Management Protocol)
traps to the open-systems host. For more information on SNMP traps and the SNMP Manager, see
the HP XP7 SNMP Agent User Guide. See
“Working with SIMs” (page 141) for more information
about SIMs.
The following figure illustrates a total pool capacity of 1 TB, Warning Threshold of 50%, and
Depletion Threshold of 80%. If the used capacity of the pool is larger than 50% (500 GB) of the
total pool capacity, a SIM and an SNMP trap are reported. If the used capacity of the pool increases
and exceeds the Depletion Threshold (80%), a SIM and an SNMP trap are reported again.
Note that in this scenario, if the actual pool usage percentage is 50.1%, only 50% appears on
the Remote Web Console window because the capacity amount is truncated after the decimal
point. If the threshold is set to 50%, a SIM and an SNMP trap are reported even though the pool
usage percentage appearing on the screen does not indicate an exceeded threshold.
Pool subscription limit
The value of using subscription limit is to manage the maximum amount of over-provisioning that
is acceptable for a pool. By managing the pool subscription limit, you can control the potential
demand for storing data that might exceed the pool capacity.
The subscription limit is the ratio (%) of the total THP V-VOL capacity that has been configured to
the total capacity of the pool. When the subscription limit is set, you cannot configure another THP
V-VOL if the new THP V-VOL capacity would cause the subscription limit to be exceeded.
The subscription limit includes pages required to store user data and control information. The total
capacity of THP V-VOLs that are created from the pool is smaller than the subscription limit capacity.
The formula used to calculate the required pages for one THP V-VOL includes the control information.
To determine the total pages required in a pool, multiply the number of calculated pages by the
number of THP V-VOLs. The value enclosed in ceil( ) must be rounded up to the nearest whole
number.
Number of pages for the THP V-VOL including the control information =
ceil((One THP V-VOL capacity (MB) + ceil(One THP V-VOL capacity (MB) /
3,145,548 (MB)) * 4 (Pages) * 42 (MB)) / 42 (MB))
For example, if the pool capacity is 100 GB and the subscription limit is 150%, you can configure
up to a total of 150 GB of capacity to the THP V-VOLs related to the pool.
Thresholds 139