HP StorageWorks XP Remote Web Console Software - Manual (Page 72)

Figure 34 RCU Option pane
Use the RCU Option pane to set the options for the RCU.
•
Minimum Paths: Minimum number of paths required for each RCU connected to the current
MCU. The default is one. If you specify a number that is larger than the number of paths set
on the Register RCU pane or the number of paths falls below this number (for example, failed
path), an error occurs. When errors occur, the MCU suspends all affected XP Continuous
Access (and any mainframe) pairs to prevent remote copy operations from adversely affecting
performance due to the inadequate number of paths. If the MCU contains XP Continuous
Access pairs, which contain critical data for disaster recovery, set minimum number of paths
to one, so XP Continuous Access operations continue even if there is only one path to an RCU.
If you need high performance at the MCU, set minimum number of paths to two or more (up
to eight per CU image), depending on number of pairs managed by the MCU.
CAUTION: If XP Continuous Access volume pairs are suspended because number of paths
dropped below this setting, the P-VOL fence-level pair option (see “Creating XP Continuous
Access volume pairs (Paircreate)” (page 99) ) determines whether XP Continuous Access
Synchronous P-VOLs are fenced (that is, all write operations are rejected).
•
RIO MIH Time: Time value for the remote I/O (RIO) missing interrupt handler (MIH), which is
the wait time until data transfer from the MCU to RCU is complete. The RIO MIH time must be
from 10 to 100 seconds. The default is 15 seconds. This setting is available for both serial
and Fibre Channel interfaces.
•
Round Trip Time (ms): Used for initial copy operations. This setting assigns priority to remote
I/O for an update copy operation. The default value is 1 ms. You can specify 1 ms to 500 ms.
During an initial copy operation, the copy pace is automatically adjusted based on the actual
time required for initial copy, which is obtained by subtracting the specified Round Trip Time
from the remote I/O response time. If the actual time required for the initial copy operation
is large, the update copy workload is relatively high. Therefore, the copy pace of the initial
copy is slowed. When the actual time is relatively small, the copy pace speeds up to the
specified value. In this way, the influence of the initial copy operation on host performance
is curbed.
NOTE: This option is available only for XP Continuous Access Sync pairs. For XP Continuous
Access Aync pairs, the value is ignored.
Use the formula described below to calculate Round Trip Time.
The formula for calculating Round Trip Time (ms) is the following:
Round Trip Time = (Round-trip time between the MCU and RCU x 2
1
) + Initial copy response time (ms)
1 Data transfer between the MCU and RCU involves two response sequences per command.
72 Performing XP Continuous Access configuration operations