HP StorageWorks P9000 User Manual page 42

15. In the Round Trip Time (ms) box, enter the time limit for data to travel from the P-VOL to the
S-VOL. This value is used by the system to control initial copy pace when update copying is
in progress.
NOTE:
throughput when the distances involved between the primary and secondary systems cause
the RIO response time to exceed 15 milliseconds.
If the difference between Round Trip Time and the initial copy pace is significant. For example,
1ms RT Time : 500ms initial copy pace, the system slows or even interrupts the initial copy
operation so that the update copy can continue.
If the difference between the two is insignificant (for example, 1ms : 5 ms) initial copying is
allowed to run at the specified pace.
To determine Round Trip Time value
The value of Round Trip time= round trip time between MCU-RCU x 2(*) + initial copy response time (ms)
(*) A data transfer between primary and secondary systems involves two response sequences in one command
issuance. Therefore, you need to double the round trip time.
For the "round trip time" in the formula, please ask your service provider, or use a ping
command. If you do not use lines between the primary and secondary systems, specify
"1."
The "initial copy response time" in the formula is the response time required for multiple
initial copy operations. You can use the following formula to get the initial copy response
time. To get the time, you should use the following: the initial copy pace, the max number
of maximum initial copy VOLs, the speed of the line between primary and secondary
systems, and the number of lines.
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 maximum initial copy VOLs (*3)" / "Number of lines between MCU-RCU"(*4))
(*1) When you connect MCU with RCU without lines, specify 0.17[MB/ms] in "Speed of line
between MCU and RCU".
(*2) For "initial copy pace" in the formula above, see the table below.
(*3) For "maximum number of maximum initial copy volumes", use the value set up per storage
system. The default is 64.
(*4) Even if "Max number of maximum copy VOLs"/"Number of lines between MCU-RCU"
is larger than 16, specify "Max number of maximum initial copy VOLs"/"Number of lines
between MCU-RCU" as 16.
Table 16 Initial copy pace used for response time calculation
Interface
RAID Manager
Remote Web
Console
42 Configuration operations
The default setting of 1 on the P9500 produces a lower than expected initial copy
Initial Copy Only in
Progress
User-specified value
User-specified value
Initial, Update Copy in Progress
When Initial Copy Pace specified
at the Time of Pair Creation is 1
to 8
User-specified value between 1
and 8
User-specified value between 1
and 8
When Initial Copy Pace specified
at the Time of Pair Creation is 9
to 15
8
8