Planning Volume Pairs; Volume Pair Requirements And Recommendations - HP StorageWorks P9000 User Manual

Table 12 Conditions affecting performance, recommendations (continued)
Condition
Capacity of remote
system
Data paths

Planning volume pairs

To plan Continuous Access Synchronous Z pair volumes, you need to do the following:
At the local site, identify the volumes that contain important data to be backed up
At the remote site, set up the volumes that will hold the copied data

Volume pair requirements and recommendations

The following requirements and information are provided to help you prepare Continuous Access
Synchronous Z volumes:
A volume can only be assigned to one Continuous Access Synchronous Z pair.
The R-VOL must be at least the same size as the M-VOL.
Continuous Access Synchronous Z requires a one-to-one relationship between the M-VOL and
R-VOL. The M-VOL cannot be copied to more than one R-VOL, and more than one M-VOL
cannot be copied to one R-VOL.
Logical Volume Images (LVIs)
All basic mainframe LVIs that can be configured on the P9500 system are supported for
◦
Continuous Access Synchronous Z; for example, 3390 3, 3R, 9, L.
Data Exchange volumes (3390 3A/B/C) are not supported.
◦
Data can be copied between volumes with the same emulation and capacity (for example,
◦
3390 3R to 3390 3R).
◦ Data can be copied from smaller volumes to larger volumes (for example, 3390 3 to
3390 9) of the same emulation (VTOC expansion must be used).
However, HP strongly recommends that you limit copying from a smaller volume to a
larger volume to data migration purposes and not disaster recovery. Under the disaster
recovery scenario, you would not be able to perform Continuous Access Synchronous Z
operations in the reverse direction, from the remote disk array to the main disk array,
because a larger volume cannot be copied to a smaller volume.
Also, with larger-to-smaller volumes, if the BCM SUSPEND command is issued, you cannot
use the remote system R/W option and Reverse option.
The following disk track format are required for pair volumes. Continuous Access Synchronous
Z cannot detect exceptions to these requirements. The main system will abort the initial copy
operation if the track format for both the M-VOL and R-VOL does not meet the following
requirements.
◦ The M-VOL and R-VOL must have the same track format.
Record zero (R0) must be standard format, with key length of zero and data length of
◦
eight. The main system will abort the initial copy operation if R0 is not standard format.
Description
The remote system's performance directly affects
the performance of the main system. If a remote
system becomes overloaded with heavy update
activity, host and main system performance can
also be degraded.
An inadequate number of data paths decreases
performance. Performing copy operations over
long distances also degrades performance.
Recommendation
Distribute Continuous Access Synchronous Z
remote copy operations among several remote
systems to avoid overloading any one system.
Install a sufficient number of data paths to will
meet all write-workload levels. This is especially
important for systems containing both M-VOLs
and R-VOLs.
Planning volume pairs 31