HP XP Racks - Manual (Page 14)

Paircreate dialog box, the remaining S-VOLs will be assigned incrementally by LUN (for
example, LUN002 and LUN003).
- Make sure that all S-VOLs to be assigned automatically are available, are numbered in
an order that will pair them properly, and that they correspond in size to the P-VOLs.
- If an S-VOL is not available for a P-VOL, the pair must be created individually.
Quorum disk requirements
Quorum disks store continually-updated information about data in ESAM P-VOLs and S-VOLs for
use during failover operations.
•
All ESAM pairs created between one MCU and one RCU must use the same quorum disk.
Thus, The P-VOL and S-VOL for a pair must use the same quorum disk.
•
A quorum disk must be located in an external storage system that is separate from the primary
and secondary storage systems.
•
Only external storage systems supported by External Storage can be used for the quorum
disk. see the HP XP P9000 External Storage for Open and Mainframe Systems User Guide
for a list of supported external systems.
NOTE: If the ESAM pair is created between P9500 and XP24000, the quorum disk must
be located in an external storage system supported by XP24000.
For a list of supported storage systems, see the HP XP 24000 External Storage User’s Guide.
•
Multiple quorum disks can be created in one external storage system.
•
The maximum number of quorum disks per external system is 128.
•
The external system is not required to be dedicated to quorum disks exclusively.
•
Quorum disk size requirements: 47 MB to 4 TB (96,000 blocks to 8,589,934,592 blocks).
•
The quorum disk must not be expanded or divided by LUN Expansion or Hitachi Virtual
LVI/LUN.
•
An LU path must not be configured to the quorum disk.
•
Read/Write operations from the storage system to the quorum disk are for internal use. These
operations are performed even when Write Pending operations reach 70%.
CAUTION: Quorum disks are used in a unique way in that they are shared with two storage
systems. For data protection reasons, make sure not to share any other kind of volume with two
storage systems.
Data path requirements and recommendations
Data is transmitted from the P-VOL to the S-VOL over the data path. Please observe the following
requirements and recommendations:
•
Data path requirements for ESAM are the same as Continuous Access Synchronous
requirements.
For more information, see the HP XP P9000 Continuous Access Synchronous User Guide.
•
Do not share the data paths with Continuous Access Synchronous. Install independent data
paths for ESAM.
•
Install at least two data paths from the primary storage system to the secondary storage system,
and two data paths from the secondary storage system to the primary storage system. This
allows data transfer to continue in the event of failure one path's cables or switches.
•
Optical fibre cables are required to connect the primary and secondary storage system.
14 System implementation planning and system requirements