Dell PowerVault MD3820f - Manual (Page 157)

6. Select how to grant host access to the snapshot virtual disk. Do one of the following:
– Select Read Write and go to step 7.
– Select Read Only and click Finish to create the snapshot virtual disk. Go to step 8.
NOTE: Repositories are not required for Read Only snapshot virtual disks.
Keep these guidelines in mind when you grant host access to a snapshot virtual disk:
– Each host has its own logical unit number (LUN) address space and allows the same LUN to be
used by different host groups or hosts to access snapshot virtual disks in a storage array.
– You can define one mapping for each snapshot virtual disk in the storage array.
– Mappings are shared between controllers in the storage array.
– The same LUN cannot be used twice by a host group or a host to access a snapshot virtual disk.
You must use a unique LUN.
– An access virtual disk mapping is not required for out-of-band storage arrays.
7. Choose how you want to create the repository for the Read-Write snapshot virtual disk. Do one of
the following:
– Select Automatic and click Finish to create the snapshot virtual disk repository with the default
capacity settings. This option is the recommended one.
– Select Manual and click Next to define the properties for the snapshot virtual disk repository.
Then click Finish to continue with the snapshot virtual disk creation procedure.
Use this option if you want to specify all of the customizable settings for the snapshot virtual disk
repository. The Manual method is considered advanced and only those who understand physical disk
redundancy and optimal physical disk configurations should use this method.
8. Click Finish.
The snapshot virtual disk and its properties under the individual virtual disk node for the associated
base virtual disk is displayed in the navigation tree. The snapshot virtual disk is added as a new virtual
disk that contains the snapshot image information, which is the data of the virtual disk at the
particular time of snapshot image creation.
Creating A Snapshot Virtual Disk Repository
When you create a snapshot virtual disk that is designated as read-write, a snapshot virtual disk repository
is created to provide the host application with write access to a copy of the data contained in the
snapshot image. You can create the repository automatically using the default settings or you can
manually create the repository by defining the capacity settings for the repository.
The following guidelines apply:
• There is a minimum required capacity for a snapshot group repository which depends on your
configuration.
• When you define the capacity requirements for a repository, keep in mind any future requirements
that you may have for other virtual disks in this disk group or disk pool. Make sure that you have
enough capacity to meet your data storage needs without allocating too much capacity that takes up
the storage in your system.
• The list of repository candidates can contain both new and existing repository virtual disks. Existing
repository virtual disks are placed at the top of the list. The benefit of reusing an existing repository
virtual disk is that you can avoid the initialization process that occurs when you create a new one.
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