Create snapshot group

Supported Arrays​

This command applies to an individual DE2000H, DE4000H, DE4000F, DE6000H, or DE6000F storage array.

Roles​

To execute this command on an storage array, you must have the Storage Admin role.

Context​

A snapshot group contains a sequence of snapshot images of an associated base volume. A snapshot group has a repository volume that is used to save data for all of the snapshot images that are part of the snapshot group.

Syntax​

create snapGroup userLabel="<var id="GUID-9D6A5673-4624-42F3-B610-2A7D6404D2D5__V1111816" className="keyword varname">snapGroupName</var>" sourceVolume="<var id="GUID-9D6A5673-4624-42F3-B610-2A7D6404D2D5__V1455028" className="keyword varname">volumeName</var>" 
[(repositoryVolume="repos_xxxx" | 
repositoryVolume=(<var id="GUID-9D6A5673-4624-42F3-B610-2A7D6404D2D5__V1455028" className="keyword varname">volumeGroupName</var> [capacity=<var id="GUID-9D6A5673-4624-42F3-B610-2A7D6404D2D5__V1523929" className="keyword varname">capacityValue</var>]) | 
repositoryVolume=(<var id="GUID-9D6A5673-4624-42F3-B610-2A7D6404D2D5__V1455028" className="keyword varname">diskPoolName</var> [capacity=<var id="GUID-9D6A5673-4624-42F3-B610-2A7D6404D2D5__V1523931" className="keyword varname">capacityValue</var>]))] 
[repositoryFullPolicy=(failBaseWrites | purgeSnapImages)] 
[rollbackPriority=(highest | high | medium | low | lowest)] 
[repositoryFullLimit=<var id="GUID-9D6A5673-4624-42F3-B610-2A7D6404D2D5__V1438428" className="keyword varname">percentValue</var>] 
[autoDeleteLimit=<var id="GUID-9D6A5673-4624-42F3-B610-2A7D6404D2D5__V1440328" className="keyword varname">numberOfSnapImages</var>]| 
[enableSchedule=(TRUE | FALSE)] 
[schedule (immediate | <var id="GUID-9D6A5673-4624-42F3-B610-2A7D6404D2D5__V1320809" className="keyword varname">snapshotSchedule</var>)]

Parameters​

Notes​

Each snapshot group name must be unique. You can use any combination of alphanumeric characters, underscore (_), hyphen (-), and pound (#) for the user label. User labels can have a maximum of 30 characters.

To create a snapshot group, you must have an associated repository volume in which you store the snapshot images. You can either use an existing repository volume or create a new repository volume. You can create the repository volume when you create the snapshot group. A snapshot group repository volume is an expandable volume that is structured as a concatenated collection of up to 16 standard volume entities. Initially, an expandable repository volume has only a single element. The capacity of the expandable repository volume is exactly that of the single element. You can increase the capacity of an expandable repository volume by attaching additional standard volumes to it. The composite expandable repository volume capacity then becomes the sum of the capacities of all of the concatenated standard volumes.

A snapshot group has a strict ordering of snapshot images based on the time that each snapshot image is created. A snapshot image that is created after another snapshot image is a successor relative to that other snapshot image. A snapshot image that is created before another snapshot image is a predecessor relative to that other one.

A snapshot group repository volume 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 volume.

The minimum capacity is enforcement by the controller firmware and the storage management software.

When you first create a snapshot group, it does not contains any snapshot images. When you create snapshot images, you add the snapshot images to a snapshot group. Use the create snapImage command to create snapshot images and add the snapshot images to a snapshot group.

A snapshot group can have one of these states:

• Optimal – The snapshot group is operating normally.
• Full – The snapshot group repository is full. Additional copy-on-write operations can not be performed. This state is possible only for snapshot groups that have the Repository Full policy set to Fail Base Writes. Any snapshot group in a Full state causes a Needs-Attention condition to be posted for the storage array.
• Over Threshold – The snapshot group repository volume usage is at or beyond its alert threshold. Any snapshot group in this state causes a Needs-Attention condition to be posted for the storage array.
• Failed – The snapshot group has encountered a problem that has made all snapshot images in the snapshot group unusable. For example, certain types of repository volume failures can cause a Failed state. To recover from a Failed state use the revive snapGroup command.

Automatic snapshot image deletion​

You can configure each snapshot group to automatically delete the snapshot images by using the autoDeleteLimit parameter. Automatically deleting the snapshot images enables you to avoid having to routinely, manually delete the images that you do not want and that might prevent the creation of future snapshot images because the repository volume is full. When you use the autoDeleteLimit parameter it causes the storage management software to automatically delete snapshot images, starting with the oldest. The storage management software deletes snapshot images until it reaches a number of snapshot images that is equal to the number that you enter with autoDeleteLimit parameter. When new snapshot images are added to the repository volume, the storage management software deletes the oldest snapshot images until the autoDeleteLimit parameter number is reached.

Scheduling snapshots​

The enableSchedule parameter and the schedule parameter provide a way for you to schedule creating snapshot images for a snapshot group. Using these parameters, you can schedule snapshots daily, weekly, or monthly (by day or by date). The enableSchedule parameter turns on or turns off the ability to schedule snapshots. When you enable scheduling, you use the schedule parameter to define when you want the snapshots to occur.

This table explains how to use the options for the schedule parameter:

This table explains how to use the timeZone parameter:

The code string for defining a schedule is similar to these examples:

enableSchedule=true schedule startTime=14:27

            

enableSchedule=true schedule scheduleInterval=180

            

enableSchedule=true schedule timeZone=GMT-06:00

            

enableSchedule=true schedule timeZone="America/Chicago"

            

If you also use the scheduleInterval option, the firmware chooses between the timesPerDay option and the scheduleInterval option by selecting the lowest value of the two options. The firmware calculates an integer value for the scheduleInterval option by dividing 1440 by the scheduleInterval option value that you set. For example, 1440/180 = 8. The firmware then compares the timesPerDay integer value with the calculated scheduleInterval integer value and uses the smaller value.

To remove a schedule, use the delete volume command with the schedule parameter. The delete volume command with the schedule parameter deletes only the schedule, not the snapshot volume.