Preparing Host Servers To Create The Snapshot Using The Advanced Path - Dell PowerVault MD3260i Administrator's Manual

• Capacity Allocation — This parameter allows you to choose where to create the snapshot repository virtual
disk. You can allocate capacity by using one of the following methods:
– Use free capacity on the same disk group where the source virtual disk resides.
– Use free capacity on another disk group.
– Use unconfigured capacity and create a new disk group for the snapshot repository virtual disk.
– It is recommended placing the snapshot repository virtual disk within the disk group of the source virtual
disk. This ensures that if drives associated with the disk group are moved to another storage array, all
the virtual disks associated with the snapshot virtual disk remain in the same group.
• Snapshot Repository Virtual Disk Capacity — The snapshot repository virtual disk capacity is expressed as a
percentage of the source virtual disk capacity. The maximum percentage allowed is 120 percent.
• Percent Full—When the snapshot repository virtual disk reaches the user-specified repository full percentage
level, the event is logged in the Major Event Log (MEL). The default snapshot repository full percentage level is
50% of the source virtual disk.
• Snapshot Repository Virtual Disk Full Conditions — Choose whether to fail writes to the source virtual disk or fail
the snapshot virtual disk when the snapshot repository virtual disk becomes full.
• Host-to-Virtual Disk Mapping — Choose whether to map the snapshot virtual disk to a host or host group now or
to map the snapshot virtual disk later. The default setting is Map later.

Preparing Host Servers To Create The Snapshot Using The Advanced Path

• Before using the Snapshot Virtual Disks Premium Feature in a Microsoft Windows clustered configuration, you
must first map the snapshot virtual disk to the cluster node that owns the source virtual disk. This ensures that
the cluster nodes correctly recognize the snapshot virtual disk.
• Mapping the snapshot virtual disk to the node that does not own the source virtual disk before the Snapshot
enabling process is completed can result in the operating system mis-identifying the snapshot virtual disk. This,
in turn, can result in data loss on the source virtual disk or an inaccessible snapshot.
• For details on mapping the snapshot virtual disk to the secondary node, see the documentation on storage
arrays with Microsoft Windows Server Failover Clusters at support.dell.com/manuals.
The destination of a snapshot repository virtual disk is determined based on the free capacity available in the disk group.
A snapshot repository virtual disk requires a minimum of 8 MB free capacity. You can choose your preferred creation
path—simple or advanced—if the disk group of the source virtual disk has the required amount of free space.
If 8 MB of free capacity is not available in the disk group of the source virtual disk, the Create Snapshot Virtual Disks
feature defaults to the advanced path. See
NOTE: You can create concurrent snapshots of a source virtual disk on both the source disk group and on another
disk group.
Before creating a Snapshot Virtual Disk, note that:
• The following types of virtual disks are not valid source virtual disks:
– Snapshot repository virtual disks
– Snapshot virtual disks
– Target virtual disks that are participating in a virtual disk copy
NOTE: Virtual Disk Copy is an Advanced (Premium) feature.
• You cannot create a snapshot of a virtual disk that contains unreadable sectors.
• You must satisfy the requirements of your host operating system for creating snapshot virtual disks. Failure to
meet the requirements of your host operating system results in an inaccurate snapshot of the source virtual disk
or the target virtual disk in a virtual disk copy.
Creating A Snapshot Virtual Disk Using The Advanced Path.
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