Dell PowerVault MD 32XX/36XX Series Storage Arrays CLI Guide

Changing The Pre-read Consistency Check Setting Of An Overall Repository Virtual Disk

Use the Pre-Read Consistency Check option to define a storage array's capability to pre-read an overall repository virtual disk consistency information and determine whether the data of that overall repository virtual disk is consistent. An overall repository virtual disk that has this feature enabled returns read errors if the data is determined to be inconsistent by the RAID controller module firmware.

You can enable this option for overall repository virtual disks that contain consistency information. RAID Level 1, RAID Level 5, and RAID Level 6 maintain redundancy information.

You can change the Pre-Read Consistency Check for an overall repository for the following storage objects:

Snapshot group
Snapshot virtual disk
Consistency group member virtual disk
Replicated Pair

This command defines the properties for a virtual disk. You can use most parameters to define properties for one or more virtual disks. You can also use some parameters to define properties for only one virtual disk. The syntax definitions are separated to show which parameters apply to several virtual disks and which apply to only one virtual disk.

NOTE: In configurations where disk groups consist of more than 32 virtual disks, the operation can result in host I/O errors or internal RAID controller module reboots due to the expiration of the timeout period before the operation completes. If you experience host I/O errors or internal RAID controller module reboots, quiesce the host I/O and try the operation again.

Syntax Applicable To One Or More Virtual Disks

set (allVirtualDisks | virtualDisk ["
                                 virtualDiskName"] | virtualDisks ["
                                 virtualDiskName1" ... "
                                 virtualDiskNameN"] | virtualDisk <wwID>)
                                 cacheFlushModifier=cacheFlushModifierValue cacheWithoutBatteryEnabled=(TRUE | FALSE)
                                 mediaScanEnabled=(TRUE | FALSE)
                                 replicationCacheEnabled=(TRUE | FALSE)
                                 modificationPriority=(highest | high | medium | low | lowest)
                                 owner=(0 | 1)
                                 preReadConsistencyCheck=(TRUE | FALSE)
                                 readCacheEnabled=(TRUE | FALSE)
                                 writeCacheEnabled=(TRUE | FALSE)
                                 cacheReadPrefetch=(TRUE | FALSE)

Syntax Applicable To Only One Virtual Disk

set (virtualDisk ["
                                 virtualDiskName"] | virtualDisk <wwID>) addCapacity=virtualDiskCapacity
                                 [addPhysicalDisks=(enclosureID1,drawerID1,slotID1 ... enclosureIDn,drawerIDn,slotIDn)]
                                 consistencyCheckEnabled=(TRUE | FALSE) segmentSize=segmentSizeValue userLabel=virtualDiskName
                                 preReadConsistencyCheck=(TRUE | FALSE)

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.

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Dell PowerVault MD 32XX/36XX Series Storage Arrays CLI Guide

Changing The Pre-read Consistency Check Setting Of An Overall Repository Virtual Disk

Syntax Applicable To One Or More Virtual Disks

Syntax Applicable To Only One Virtual Disk

preReadConsistencyCheck

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