Designing Disaster Tolerant High Availability Clusters, 10th Edition, March 2003 (B7660-90013)

Building an Extended Distance Cluster Using MC/ServiceGuard
Two Data Center Architecture
Chapter 2 53
StorageWorks Disk Array XP or EMC Symmetrix Disk Arrays. If
Model FC30 disk arrays are used as cluster lock disks, Auto trespass
must be disabled for the entire disk array.
• Application data must be mirrored between the primary data
centers. If MirrorDisk/UX is used, Mirror Write Cache (MWC) must
be the Consistency Recovery policy defined for all mirrored logical
volumes. This will allow for resynchronization of stale extents after
a failure of a mirror copy, rather than requiring a full
resynchronization. You must ensure that the mirror copies reside in
different data centers, so it is recommended to configure physical
volume groups for the disk devices in each data center, and to use
Group Allocation Policy for all mirrored logical volumes.
• Due to the maximum of 3 disk images (one original and two mirror
copies) allowed in MirrorDisk/UX, if JBODs are used for application
data, only one data center can contain JBODs while the other data
center must contain disk arrays with hardware mirroring.
• No routing is allowed for the networks between data centers.
Routing is allowed to the third data center if a Quorum Server is
used in that data center.
• VERITAS Volume Manager (VxVM) mirroring is supported for
clusters of 2 or 4 nodes. However, the cluster lock devices must still
be configured in LVM Volume Groups. The maximum distance
supported for VxVM is 10 kilometers. You must ensure that the
mirror copies reside in different data centers, and the DRL (Dirty
Region Logging) feature must be used. Raid 5 mirrors are not
supported.
• VERITAS Cluster Volume Manager (CVM) mirroring is supported
for MC/ServiceGuard or ServiceGuard OPS Edition clusters
containing 2 or 4 nodes. However, the dual cluster lock devices must
still be configured in LVM Volume Groups.