HP XP P9500 Storage - Manual (Page 24)

A Controlling the amount of write data
This appendix describes how to control the amount of write data the storage system performs
according to the sidefile capacity.
When block option is set to cache level
When the Cache Level 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 (i.e., 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 (i.e., 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.
Figure 12 Controlling the Amount of Write Data (1)
When do not block (volume level) option is set to disable
When the Do not 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 per volume. The threshold is specified by SDM;
24 Controlling the amount of write data