Asynchronous Copy Option - HP xp12000 User Manual

Async options apply to the entire physical control unit, including all Continuous Access XP P-VOLs and
S-VOLs behind the control unit.
Figure 42 Async Option pane
All default settings indicate the current settings.
• Pending Update Data Rate (%): Continuous Access XP Asynchronous sidefile threshold, which is
maximum amount of cache that can be used for storing Continuous Access XP Async recordsets
(sidefiles). Select any value between 30% and 70% (10% increments) (see
recordsets" on page 22).
The current pending update data rate is common to both Continuous Access XP and TC390 operations.
The most recently entered value is applied to all Continuous Access XP Async operations.
If one or more consistency groups exist, this setting cannot be changed. This setting can only be
changed when no CT groups are assigned.
You can specify the Pending Update Data Rate from the Async Option pane of TC390. If the specified
Pending Update Data Rate is less than the I/O Delay Start or I/O Delay Increase specified from the
Async Option pane of Continuous Access XP, the Pending Update Data Rate is available.
• Offloading Timer (sec.): Amount of time (0-255 seconds) the MCU waits to send a Continuous Access
XP Async recordset to the RCU. The MCU suspends all affected Continuous Access XP Async volume
pairs if it cannot offload a recordset to the RCU within the specified time (for example, the RCU is still
responding channel-command-retry).
The offloading timer should be set to less than the HBA I/O timeout value.
When channel-extenders are used for Continuous Access XP Async, the offloading timer should be set
to 35 seconds or less to avoid affecting host I/O performance.
• I/O Delay Start: Threshold (0-70%), which is maximum amount of cache for starting inflow control for
the asynchronous copy. When amount of cache used for async recordsets reaches the specified
threshold, the MCU controls the cache inflow.
• I/O Delay Increase: Threshold (0-70%), which is maximum amount of cache for starting to strengthen
control over inflow for the asynchronous copy. When amount of cache used for async recordsets
reaches the specified threshold, the MCU controls cache inflow.
NOTE: Specify a value not exceeding the I/O Delay Increase for the I/O Delay Start. Specify a value not
exceeding the Pending Update Data Rate for the I/O Delay Increase. If sidefile threshold is set between 0
to 30%, influence to the I/O delay is kept low.
82 Continuous Access XP for the XP12000/XP10000
"Inflow control of