62 Preparing Your Systems for Clustering
Snapshot Virtual Disk
Snapshot Virtual Disk captures point-in-time images of a virtual disk for
backup, testing, or data processing without affecting the contents of the
source virtual disk. You can use either Simple Path or Advanced Path to
create a snapshot for your cluster disk. The Snapshot Virtual Disk can be
mapped to the primary node (the node owning the source disk) or the
secondary node (the node not owning the source disk) for backup, testing, or
data processing.
CAUTION: Avoid mapping the Snapshot Virtual Disk to more than one node in the
cluster at any point of time. The Snapshot Virtual Disk is not managed by Failover
Cluster Manager, so mapping the Snapshot Virtual Disk to the host group or both
nodes in the cluster may allow both nodes to access data concurrently and thus
cause data corruption.
You can use a Microsoft Volume Shadow-copy Service (VSS) application to
create and map snapshots. If you are using MDSM instead, you must follow
the procedures described below.
To map the Snapshot Virtual Disk to the primary node:
1
Use Host-to-Virtual Disk Mapping in the Modular Disk Storage Manager.
This ensures that a different disk signature is assigned properly to the
Snapshot Virtual Disk.
2
Use Windows Disk Management to re-scan for the Snapshot Virtual Disk,
assign the drive letter, and start accessing the drive.
NOTE: The disks may be re-scanned several times for the Snapshot Virtual
Disk to be detected by Windows Disk Management. If the Snapshot Virtual
Disk is not detected, wait for a few minutes and re-scan the disks. Repeat the
process until the Snapshot Virtual Disk is detected; do not reboot the server.
If you need to map the Snapshot Virtual Disk to the secondary node (the
node not owning the source disk), you must map the Snapshot Virtual Disk to
the primary node first, to ensure that the snapshot is assigned a new disk
signature. Then, use Modular Disk Storage Manager to unmap the Snapshot
Virtual Disk from the primary node, map it to the secondary node, and start
accessing it.
CAUTION: Attempts to map the Snapshot Virtual Disk to the secondary node, prior
to obtaining the signature from the primary node, may cause the operating system
to misidentify the Snapshot Virtual Disk as an existing system volume and that may
result in data loss or an inaccessible Snapshot Virtual Disk.
book.book Page 62 Monday, June 21, 2010 1:45 PM
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