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

Create Consistency Group

NOTE: This command does not apply to the snapshot (legacy) commands.

Description

This command creates a new, empty consistency group that can contain snapshot groups. You must add the snapshot groups using the set consistencyGroup addCGMember command.

Syntax

create consistencyGroup userLabel=
                                 "consistencyGroupName" [repositoryFullPolicy=(failBaseWrites repositoryFullLimit=
                                 percentValue |
                                 autoDeleteLimit=
                                 numberOfSnapImages |
                                 enableSchedule=(TRUE | FALSE) |
                                 schedule (immediate | 
                                 snapSchedule) |
                                 rollbackPriority=(lowest | low | medium | high | highest)]

Parameters

Parameter	Description
`userLabel`	The name of the new consistency group that you want to create. Enclose the new consistency group name in double quotation marks (" ").
`repositoryFullPolicy`	How you want snapshot processing to continue if the snapshot repository virtual disks are full. You can choose to fail writes to the base virtual disk ( `failBaseWrites`) or delete (purge) the snapshot images ( `purgeSnapImages`). The default action is `purgeSnapImages`.
`repositoryFullLimit`	The percentage of repository capacity at which you receive a warning that the snapshot repository virtual disk is nearing full. Use integer values. For example, a value of `70` means 70 percent. The default value is `75`.
`autoDeleteLimit`	The maximum number of snapshot images that you want to automatically delete if you have selected to purge the snapshot images for a repository full policy. The default value is `32`.
`enableSchedule`	Whether the ability to schedule a snapshot operation is turned on or turned off. To turn on snapshot scheduling, set this parameter to `TRUE`. To turn off snapshot scheduling, set this parameter to `FALSE`.
`schedule`	Use this parameter to schedule a snapshot operation. You can use one of these options for setting a schedule for a snapshot operation: `immediate` `startDate` `scheduleDay` `startTime` `scheduleInterval` `endDate` `timesPerDay` `timeZone` See the Notes section for information explaining how to use these options.
`rollBackPriority`	Determines whether system resources should be allocated to the rollback operation at the expense of system performance. A value of high indicates that the rollback operation is prioritized over all other host I/O. A value of `low` indicates that the rollback operation should be performed with minimal impact to host I/O.

Notes

A consistency group is a logical entity that enables you to manage in batch form all of the snapshot images that you add to the collection. The consistency group is a collection of snapshot groups that have mutual consistency requirements or dependencies for their snapshot images. Any snapshot images that you create and use for this collection must be managed in accordance with the consistency dependencies.

You can use any combination of alphanumeric characters, underscore (_), hyphen (-), and pound (#) for the names. Names can have a maximum of 30 characters.

The snapshot images in a consistency group can be deduced based on the existence of a snapshot image within a consistency group. All snapshot images that reside within a consistency group share a common time stamp and sequence number.

An operation on a snapshot image consistency group is treated as a single request, and causes all pending I/O operations to the associated base virtual disk of each member to be drained and suspended before creating the snapshot images. If creation of the snapshot images cannot be completed successfully for all of the consistency group members, the operation fails and has no affect (that is, new snapshot images are not created).

Based on this behavior all members for a consistency group usually have the same number of PiTs. However, when a new member is added to a consistency group, that new member lacks the snapshot images that were previously created on the established members of the consistency group. This is not considered an error condition. Ensuing requests for deletion or rollback of snapshot images that only exist on a subset of the consistency group members will only affect the members for which the specified snapshot images actually exists.

For more information on scheduling snapshot images in a consistency group, see Scheduling Snapshots .

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