Dell PowerVault MD3260i - Manual (Page 60)

preReadConsistencyCheck
The setting to turn on or turn off preread consistency checking. Turning on preread consistency checking verifies the
consistency of RAID redundancy data for the stripes containing the read data. Preread consistency checking is
performed on read operations only. To turn on preread consistency checking, set this parameter to TRUE. To turn off
preread consistency checking, set this parameter to FALSE.
NOTE: Do not use this parameter on non-redundant virtual disks, such as RAID 0 virtual disks.
Guidelines while using the Pre-Read Consistency Check option:
• Changing the Pre-Read Consistency Check setting modifies the setting only for the overall repository that you
selected.
• The Pre-Read Consistency Check setting is applied to all individual repository virtual disks contained within the
overall repository.
• If an overall repository virtual disk that is configured with pre-read is migrated to a RAID level that does not
maintain consistency information, the metadata of the overall repository virtual disk continues to show that pre-
read is enabled. However, reads to that overall repository virtual disk ignores consistency pre-read. If the virtual
disk is subsequently migrated back to a RAID level that supports consistency, the option becomes available
again.
NOTE: Enabling the option on overall repository virtual disks without consistency does not affect the virtual disk.
However, the attribute is retained for that overall repository virtual disk if it is ever changed to one with
consistency information.
Setting Snapshot Virtual Disk Repository Virtual Disk Capacity
To increase or decreases the capacity of a snapshot virtual disk repository virtual disk, use the set
snapVirtualDisk command.
A snapshot repository virtual disk is an expandable virtual disk that is structured as a concatenated collection of up to 16
standard virtual disk entities. Initially, an expandable repository virtual disk has only a single element. The capacity of
the expandable repository virtual disk is exactly that of the single element. You can increase the capacity of an
expandable repository virtual disk by attaching additional standard virtual disks to it. The composite expandable
repository virtual disk capacity then becomes the sum of the capacities of all of the concatenated standard virtual disks.
A snapshot group repository virtual disk must satisfy a minimum capacity requirement that is the sum of the following:
• 32 MB to support fixed overhead for the snapshot group and for copy-on-write processing.
• Capacity for rollback processing, which is 1/5000th of the capacity of the base virtual disk.
If you are creating a new repository virtual disk when you run this command, you must enter the name of a disk group or
disk pool from which you want the repository virtual disk. Optionally, you can also define the capacity of the repository
virtual disk. The following capacity values are supported:
• A percentage ( integer value) representing an amount of the base virtual disk capacity.
• A decimal fraction representing a percentage of the base virtual disk capacity.
• A specific size for the repository virtual disk, in units of bytes, KB, MB, GB, or TB.
To increase capacity for a snapshot virtual disk, use the increaseRepository Capacity and capacity
parameter as shown below:
set snapVirtualDisk[“snapVirtualDiskName”] increaseRepositoryCapacity
repositoryVirtualDisks=("repos_xxxx" | repositoryVirtualDisks=(diskGroupName
[capacity=capacityValue]) repositoryVirtualDisks=(diskPoolName
[capacity=capacityValue]))
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