HP StorageWorks XP Remote Web Console Software - Manual (Page 20)

The RCU accepts only the recordset with the sequence number required to continue settling pending
recordsets. If the RCU cannot settle a recordset within the user-specified offloading timer value, the
RCU suspends all XP Continuous Access Asynchronous volume pairs and resets the
channel-command-retry condition to avoid hanging up the MCU.
Table 5 (page 20) shows sidefile threshold values for XP Continuous Access Asynchronous operations
and write pending operations and describes the actions that occur when each threshold is reached.
Table 5 Sidefile thresholds
Actions Thresholds Operation
MCU reaches threshold: I/O delay starts. If
sidefile threshold is set between 0 and 30%,
influence to the I/O delay is kept low.
RCU reaches threshold: No action.
I/O Delay Start (threshold) = 30%
Use XP Continuous Access to adjust threshold
to desired value between 0 and 70% in 1%
increments. Specify a value not exceeding
the value of I/O Delay Increase, and Sidefile
threshold.
XP Continuous Access
Asynchronous
MCU reaches threshold: I/O delay increases.
If sidefile threshold is set between 0 and 30%,
influence to the I/O delay is kept low.
RCU reaches threshold: No action.
I/O Delay Increase (threshold) = 40%
Use XP Continuous Access to adjust threshold
to desired value between 0 and 70% in 1%
increments. Specify a value within the range
of the I/O Delay Start threshold and Sidefile
threshold.
XP Continuous Access
Asynchronous
MCU reaches threshold: I/O delay.
RCU reaches threshold: Command retry to
MCU.
Sidefile threshold = 50%
Use XP Continuous Access to adjust threshold
(30, 40, 50, 60, or 70%).
XP Continuous Access
Asynchronous
Command retry. [write pending] / [avail cache - sidefile] =
70% Write Pending
Cache LUN XP operations might decrease total amount of cache available for XP Continuous
Access Asynchronous operations, but they do not directly affect sidefile cache usage. Available
cache is the amount of physical cache memory installed on the disk array minus any cache reserved
for the Cache LUN XP feature.
If you do not want to control inflow into a sidefile, specify the value of the Pending Update Data
Rate for the I/O Delay Start and I/O Delay Increase, and specify 0 seconds for the Offloading
Timer.
XP Continuous Access Synchronous consistency group operations
To specify a consistency group for XP Continuous Access Synchronous pairs, create XP Continuous
Access Synchronous pairs and execute operations on them using XP RAID Manager. Once a
consistency group for XP Continuous Access Synchronous pairs is specified, issue the commands
for each consistency group and maintain the consistency of the pairs in the same group.
For details about creating the pair and specifying consistency groups for XP Continuous Access
Synchronous, and for information regarding the operation of these consistency groups, see the HP
StorageWorks XP RAID Manager User's Guide.
20 Overview of XP Continuous Access operations