HP StorageWorks XP Remote Web Console Software - Manual (Page 53)

storage system cache should be configured to adequately support the XP Continuous Access remote
copy workloads, as well as any local workload activity.
Host Failover Software
The storage system program products do not provide any host failover functions for disaster recovery.
Host failover software is a critical component of any disaster recovery effort. When an MCU fails
to maintain synchronization of an XP Continuous Access pair, the MCU generates sense information.
It is very important that this information be transferred to the remote site via the host failover software
for effective disaster recovery.
Duplicate Volumes
Since the contents of the P-VOL and S-VOL of an XP Continuous Access pair are identical, the
S-VOL can be considered a duplicate of the P-VOL. Since the host operating system (OS) does not
allow duplicate volumes, the host system administrator must take precautions to prevent system
problems related to duplicate volumes. You must define the XP Continuous Access S-VOLs so they
do not auto-mount or come online to the same host at the same time as the P-VOLs (see Caution
below).
XP Continuous Access does not allow the S-VOL to be online (except when the pair is split). If the
S-VOL is online, the XP Continuous Access paircreate operation will fail.
CAUTION: If the XP Continuous Access S-VOLs are physically attached to the same host server(s)
as the XP Continuous Access P-VOLs, the following problem can occur:
When an XP Continuous Access pair is released, the old S-VOL is usually offline. If the host is then
restarted, the system administrator may be offered both volumes and asked which volume should
be left offline. This can be confusing and is prone to error.
If the XP Continuous Access S-VOLs and P-VOLs are connected to the same host(s), HP strongly
recommends that the S-VOLs be defined to remain offline to avoid this problem.
Host System Crash
The contents of the P-VOL and S-VOL of an XP Continuous Access pair may become inconsistent
if the host system hangs (crashes) while a write operation is being performed on the XP Continuous
Access P-VOL, and the write operation cannot be retried because of the following reasons:
•
A check condition is reported to the host due to a failure in the storage system when the write
command for the XP Continuous Access pair is issued.
•
A reset command is issued from the host and the write operation is stopped (the write operation
is incomplete).
If these conditions occur, you must retry the job to complete the write operation.
Installing the Hardware
Initial installation of the XP Continuous Access hardware is performed by the user and HP Technical
Support representative. The hardware configurations for XP Continuous Access Synchronous and
XP Continuous Access Asynchronous are the same.
To install the hardware required for XP Continuous Access operations:
1. User: Identify the locations of the XP Continuous Access primary and secondary volumes
(P-VOLs and S-VOLs), so that the XP Continuous Access hardware can be installed and
configured properly.
2. HP Technical Support Representative: Make sure that the MCU(s) and RCU(s) are configured
for Remote Web Console operations (for example, SVP connected to LAN). See the HP
Installing the Hardware 53