HP XP7 Storage - Manual (Page 29)

A Controlling the amount of write data
This topic describes how to control the amount of write data the storage system performs according
to the sidefile capacity.
When the Donot Block option is enabled
When the Cache Level Donot Block option is selected, depending on the sidefile capacity, the
storage system performs one of the following three levels for controlling the amount of write data.
•
Level 1: This level of control is performed when the sidefile capacity is equal to or larger than
the level-1 threshold, and is smaller than the level-2 threshold.
When Level 1 Sleep is set to Enable, write I/Os to volumes are put in a wait status by command
retry when the sleep wait threshold (that is, level-1 threshold) is exceeded.
When Level 1 Sleep is set to Disable, write I/Os to volumes will not be put in a wait status.
•
Level 2: This level of control is performed when the sidefile capacity is equal to or larger than
the level-2 threshold, and is smaller than the level-3 threshold.
When Level 2 Suspend is set to Disable, write I/Os to volumes are put in a wait status by
SCP-SCI reporting when the SCP-SCI reporting threshold (that is, level-2 threshold) is exceeded.
When Level 2 Suspend is set to Enable, the storage system will not report SCP-SCI to hosts.
Sidefile puncture will occur and the target session will be suspended. Sidefile puncture is the
sidefile threshold plus 10%.
•
Level 3: This level of control is performed when the sidefile capacity is equal to or larger than
the level-3 threshold.
Sidefile puncture can occur. The session for the sidefile, containing the maximum capacity in
the cache in the CLPR, is suspended.
The following figure shows levels of controlling write data when the Donot Block option is set to
cache level.
When the Donot Block option is disabled
When the Donot Block option is disabled, depending on the sidefile capacity, the storage system
performs one of the following four levels of control of the amount of write data.
•
Level 0: This level of control is performed when the sidefile capacity is smaller than the level-1
threshold.
When Level 1 Sleep is set to Enable, write I/Os to volumes are put in a wait status according
to the threshold for the number of record sets for each volume. The threshold is specified by
When the Donot Block option is enabled 29