Managing snapshots using IBM Spectrum Scale GUI

Use Files > Snapshots page in the IBM Spectrum Scale GUI to manage snapshots through GUI.

Snapshots can be used in environments where multiple recovery points are necessary. A snapshot can be taken of file system or fileset data and then the data can be recovered from the snapshot if the production data is not available.
Note:
  • Snapshots are read-only; changes can be made only to the normal and active files and directories, not to the snapshot.
  • When a snapshot of an independent fileset is taken, only nested dependent filesets are included in the snapshot.

Scheduling snapshot creation by using snapshot rules

You can either manually create the snapshots or create snapshot rules to automate the snapshot creation and retention through the IBM Spectrum Scale GUI. You cannot schedule snapshot creation if you create snapshots by using the mmcrsnapshot CLI command. However, you can use the GUI CLI command options that are available at the following directory on the GUI node to schedule snapshot creation: /usr/lpp/mmfs/gui/cli.

To manually create a snapshot, click Create Snapshot in the Snapshots page and enter the necessary details under the Manual tab of the Create Snapshot window. Click Create after entering the details.

By creating a snapshot rule, you can automate the snapshot creation and retention. That is, in a snapshot rule you can specify a frequency in which the snapshots must be created and the number of snapshots that must be retained for a period. The retention policy helps to avoid unwanted storage of snapshots that result in waste of storage resources.

Retention policy has the following parameters:
  • Frequency of snapshot creation
  • Number of most recent snapshots to be retained. The most recent snapshot is identified based on the frequency of snapshot creation.
  • Number of days for which you need to keep the latest snapshot of each day.
  • Number of weeks for which you need to keep the latest snapshot of each week.
  • Number of months for which you need to keep the latest snapshot of each month.

Example scenario for retention policy

The following table provides an example for the values that are specified against these parameters.
Table 1. Example for retention period
Frequency Minute Number of most recent snapshots Keep latest snapshots for
Hours Days Weeks Months
Hourly 1 2 2 6 2 3
Based on this retention rule, the following snapshots are created and retained on 20 March 2016 at 06:10 AM.
Table 2. Example - Time stamp of snapshots that are retained based on the retention policy
Time stamp Condition based on which snapshot is retained
December 31 (Thursday, 11:01 PM) Keep latest snapshot for last 3 months.
January 31 (Sunday, 11:01 PM) Keep latest snapshot for last 3 months.
February 29 (Monday, 11:01 PM) Keep latest snapshot for last 3 months.
March 5 (Saturday, 11:01 PM) Keep latest snapshot for last 2 weeks.
March 12 (Saturday, 11:01 PM) Keep latest snapshot for last 2 weeks.
March 14 (Monday, 11:01 PM) Keep latest snapshot for last 6 days.
March 15 (Tuesday, 11:01 PM) Keep latest snapshot for last 6 days.
March 16 (Wednesday, 11:01 PM) Keep latest snapshot for last 6 days.
March 17 (Thursday, 11:01 PM) Keep latest snapshot for last 6 days.
March 18 (Friday, 11:01 PM) Keep latest snapshot for last 6 days.
March 19 (Saturday, 11:01 PM) Keep latest snapshot for last 6 days.
March 20 (Sunday, 5: 01 AM) Keep 2 most recent.
March 20 (Sunday, 6: 01 AM) Keep 2 most recent.

According to this rule, 13 snapshots are retained on 20 March 2016 at 06:10 AM.

To schedule snapshot creation and retention, follow the procedure that is shown:
  1. Go to Files > Snapshots.
  2. Click Create Snapshot.
  3. In the Create Snapshot window, enter the path of the file system or independent fileset for which you need to create snapshots.
  4. In the Snapshot name field, specify the name of the snapshot.
  5. Click Snapshot Rules.
  6. Click Create Rule to schedule the snapshot creation and retention. Create Snapshot Rule window is displayed.
  7. In the Name field, type the name of the snapshot scheduling rule.
  8. In the Frequency field, select the frequency in which you need to create snapshot. You need to enter some more details based on the value that is selected in the Frequency field. For example, if value selected is Multiple Times an Hour, select the minutes of the hour in which you need to create snapshots.
  9. In the Retention fields, specify the number of snapshots that must be retained in a time period.
  10. In the Prefix field, specify a prefix to be added with the name of the snapshots that are created with this rule.
  11. Start of changeSelect the Allow Expiration checkbox to delete the snapshot when the defined retention period is completed.
    Note: If you do not select the Allow Expiration checkbox then the expiration time for all snapshots created is the same as its creation time.
    End of change
  12. Click OK to save the changes.

If you do not specify a name for the snapshot, the default name is given. The default snapshot ID is generated at the creation time by using the format "@GMT-yyyy.MM.dd-HH.mm.ss". If this option is given and the "@GMT-date-time" format is omitted, then this snapshot is not identified by Windows VSS and the file restore is not possible by that method. Avoid white spaces, double and single quotation marks, the parentheses (), the star *, forward slash /, and backward slash \.

Deleting snapshots

To manually delete the snapshots, right-click the snapshot from the Snapshots page and select Delete. The snapshots that are automatically created based on the snapshot creation rule, are deleted automatically based on the retention period that is specified in the rule. When the condition for deletion is met, the GUI immediately starts to delete the snapshot candidates.
Note: Start of changeDefault snapshots for which retention period is not defined can be deleted any time after their creation.End of change

Creating and deleting peer and RPO snapshots

The peer and recovery point objective (RPO) snapshots are used in the AFM and AFM DR configurations to ensure data integrity and availability. When a peer snapshot is taken, it creates a snapshot of the cache fileset and then queues a snapshot creation at the home site. This process ensures application consistency at both cache and home sites. The RPO snapshot is a type of peer snapshot that is used in the AFM DR setup. It is used to maintain consistency between the primary and secondary sites in an AFM DR configuration.

Use the Create Peer Snapshot option in the Files > Snapshots page to create peer snapshots. You can view and delete these peer snapshots from the Snapshots page and also from the detailed view of the Files > Active File Management page.