HP StorageWorks Continuous Access XP user guide for the XP10000/XP12000 (December 2005)

Continuous Access XP user guide for the XP10000/XP12000 67
When an initial copy operation is in progress, the copy pace is automatically adjusted based on the actual
time required for initial copy, which can be obtained by subtracting the specified Round Trip Time
(obtained using the formula below) 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 time is relatively small, the copy pace speeds up to the specified value. In
this way, the influence of the exclusive line use in the initial copy operation on the host performance is
curbed.
NOTE: This option is available only for Continuous Access XP Sync pairs. For Continuous Access XP Aync
pairs, this option value is invalid.
The default value of Round Trip Time is 1 ms. You can specify 1 ms to 500 ms. Use the following formula to
calculate the Round Trip Time:
For the Round Trip Time between the MCU and RCU, contact your carrier or use the ping command and
so on to measure the time. If you do not use lines and so on between the MCU and RCU, specify 1.
Initial copy response time is the response time required for multiple initial copy operations. Use the
following formula to calculate the initial copy response time. To obtain the time, use the following values:
• Initial copy pace
• Maximum number of initial copy VOLs
• Speed of the line between the MCU and RCU
• Number of lines
Round Trip Time = Round Trip Time between MCU-RCU x 2
1
+ Initial Copy response time (ms)
1. Data transfer between the MCU and RCU involves two response sequences per command issued. Therefore, you must double the
Round Trip Time between the MCU and RCU.
Initial Copy response time (ms) = (1[MB] / "Speed of line between MCU-RCU[MB/ms]
1
")
x ("initial copy pace"
2
/ 15)
x ("max number of initial copy VOLs
3
" / "Number of
lines between MCU-RCU"
4
)
1. When you connect the MCU and RCU without lines and so on, specify 0.17[MB/ms] in “Speed of line between MCU and
RCU.”
2. For “initial copy pace” in the formula, see Table 21.
3. For maximum number of initial copy volumes, see ”Changing subsystem settings” on page 59. The default is 64.
4. Even if “Max number of initial copy VOLs” / “Number of lines between MCU-RCU” is larger than 16, specify “Max number of
initial copy VOLs” / “Number of lines between MCU-RCU” as 16.
Table 21 Initial copy pace for calculating initial copy response time
Perform initial
copy only
Perform initial copy and update copy at one time
Initial copy pace
specified at time of pair
creation is 1 to 8
Initial copy pace
specified at time of pair
creation 9 to 15
Operation RAID Manager Initial copy pace
specified when pair
was created
Initial copy pace specified
when pair was created
8
Command View XP
or XP Remote Web
Console
Initial copy pace
specified when pair
was created
Initial copy pace specified
when pair was created
8