# Snapshots and Snapshot Policies

<a id="managing-snapshots-and-policies"></a>

## Managing Snapshots and Snapshot Policies

Snapshots are Read-Only representations of the Volume’s data set at a
given point-in-time. Snapshots are very efficiently thinly provisioned,
sharing all the unmodified data chunks with the Volume. Write ordering
is ensured at Snapshot creation, i.e. all writes that were acknowledged
to the Server by the VPSA before the Snapshot was created will be
contained in the Snapshot’s data set.

<a id="creation-deletion-of-snapshots"></a>

### Manual creation and deletion of snapshots

To manually create a snapshot:

- Go to the Volumes page, press the **Data Services** button and
  select **Create Snapshot**.
- Enter a unique name for the snapshot and confirm the operation.

To manually delete a snapshot:

- Go to the Volumes page, select the **Volume** and view the **Snapshots**
  South Panel tab to display the list of snapshots associated with this
  Volume.
- Select the snapshot to be deleted in the **Snapshots** tab and press the
  **Delete Snapshot** button at the top left corner of the South Panel.
- The snapshot will move to a Deleting state and will disappear from
  the list once the deletion process completes. Please note that
  Snapshots deletion typically takes less than a minute, but in complex
  configurations it may extend up to few minutes.

<a id="managing-snapshot-policies"></a>

### Managing Snapshot Policies

Snapshot policies define the Snapshots life cycle via the enforcement of
creation and deletion policies. Snapshot Policies are “global” entities,
and you can apply instances of the policies to one or more Volumes.
Unapplied policies are idle—they do not consume any resources and never
create any snapshots. A few points to consider:

- You can apply a Snapshot policy to one or more Volumes.
- You can apply multiple Snapshot Policies to a Volume.
- If two or more Snapshot policies are scheduled to create a Snapshot
  at the same time on the same Volume, only a single Snapshot will be
  created. That Snapshot will only be deleted when all relevant Delete
  Policies approve its deletion.
- Snapshot creation time is a “rounded” time, regardless of the precise
  policy creation time. For example, if you initialized a Snapshot
  Policy at 9:02 that has a Creation Policy to create a snapshot every
  10 minutes, the Snapshots will be created at 9:10, 9:20, 9:30 and so
  forth (not at 9:12, 9:22, 9:32, etc.).
- For the predefined snapshots policies like “Every Day” or “Every Hour”
  the Snapshot creation time is distributed on 10 minutes slots during the hour.
  The specified interval of one hour is kept, but not necessarily on the hour.
  Snapshots may be taken every hour 10 minutes after the hour, or 20 minutes
  after the hour, etc… (For example: 9:10, 10:10, 11:10 , …)
  If a precise snapshot creation time is needed, define a custom snapshot policy
  that specifies the exact time.
- You can decide whether or not empty snapshots are to be created.
  i.e. if the time has come to create a Snapshot according to the
  Creation Policy but no data has changed since the previous Snapshot,
  you can specify whether a new and empty Snapshot will be created.
  This might be useful if you want to make sure the snapshot policy is
  enforced and snapshots are taken on time regardless of the data changes.
- The following Snapshots Policies are predefined in the VPSA.

  | Name                        | Create Policy               |
  |-----------------------------|-----------------------------|
  | Hourly Snapshots for a Day  | Every hour                  |
  | Daily Snapshots for a Week  | Once per day after midnight |
  | Weekly Snapshots for a Year | Every Sunday after midnight |
  | Daily Backup for a Year     | Once per day after midnight |

#### Creating a new Snapshot Policy

1. Go to the Snapshot Polices page and press **Create**.
2. In the **Create Snapshot Policy** dialog, enter:
   - **Name** - Provide a meaningful name to the Policy.
   - **Creation Policy** – Select the appropriate policy from the drop
     down list.
   - **Deletion Policy** – Use these 2 fields to define the maximum number
     of Snapshots to retain in the Deletion Policy. If you will be using
     this policy for Remote Mirroring, you can define a different number
     of Snapshots to retain on the DR site. This field is optional and
     defaults to the above deletion policy.
   - **Allow Empty Snapshot Creation** – Select this checkbox if you’d
     like Snapshots to be created according to the Creation Policy, even
     if no data was modified since the previous Snapshot.
   - **Set as default policy for newly created volumes** – Select this
     checkbox if you’d like all new Volumes to default to this Snapshot
     Policy. Select the appropriate Creation Policy from the drop down
     list.
   - Define the number of Snapshots to retain in the deletion policy.
   - Allows Empty Snapshot Creation – Set this checkbox if you’d like
     snapshots to be created according to the creation policy even if no
     data was modified since the previous snapshot.
   - If you will be using this policy for Remote Mirroring, you can define
     a different number of Snapshots to retain on the DR site. This field
     is optional and defaults to the above deletion policy.

#### Editing a Snapshot Policy

1. Go to the Snapshot Polices page, select the Policy and press **Edit**.
2. You can edit all of the Snapshot Policy’s attributes: Name, Creation
   Policy, Deletion Policy, Allow Empty Snapshots Creation and Set as Default Policy.
3. You can modify a Snapshot Policy even when it is active on one or
   more Volumes. The modifications in the Policy’s behavior will be
   reflected on all relevant Volumes.
4. If you reduce the number of Snapshots to retain for a Snapshot Policy
   that is active on one or more Volumes, it will trigger the deletion
   of all Snapshots that no longer meet the new Deletion Policy.

#### Applying a Snapshot Policy on a Volume

1. Go to the Volumes page, select the Volume and select
   **Data Services > Attach Snapshot Policy**.
2. In the **Attach Snapshot Policy to Volume** dialog, select the
   Snapshot Policy to apply to the selected Volume, and press **Submit**.

#### Detaching a Snapshot Policy from a Volume

1. Go to the Volumes page, select the Volume and press the Snapshot
   Policies south tab to view the Volume’s applied Snapshot Policies.
2. Select the Snapshot Policy to delete and press **Detach Policy** at the
   top left corner of the South Panel.

   You will be prompted to decide whether or not to delete all the
   Volume’s Snapshots which are associated with this Policy.

#### Pausing or Resuming a Snapshot Policy

You can pause an active Volume Snapshot Policy. New Snapshots will not
be created, but existing Snapshots are not affected. Pausing a Snapshot
Policy on one Volume has no impact on other Volumes that also have this
Policy active.

* To **pause** a Snapshot Policy:
  1. Go to the :Volumes page, select the
     Volume and press the **Snapshot Policies** tab on the South Panel to
     view the Volume’s active Snapshot Policies.
  2. Select the Snapshot Policy and press **Pause Policy** at
     the top left corner of the South Panel.

     The **Policy Status** will change to **Paused**.
* To **resume** a Policy:

  Select a Policy in a **Paused** state and press **Resume Policy** at the
  top left of the South Panel.

  The **Policy Status** will change to **Active**.

<!-- When the Enterprise Suite is disabled, all active Snapshot
Policies are immediately paused, and when the Enterprise Suite is
re-enabled, policies are resumed*. -->

<a id="filtering-snapshots"></a>

## Filtering Snapshots

Snapshots can be created manually, by using Snapshot Policies,
by Remote Mirroring or by Backup to Object Store.
This can result in many Snapshots spread across multiple Volumes.

Finding a specific snapshot could therefore take some time.
The “Filter Snapshot” option will help you to find the snapshot you need more efficiently.

1. Go to The Volumes page, select a Volume and display the **Snapshots**
   tab in the South Panel.
2. Press the **Filter** button at the bottom of the page.
3. In the resulting dialog, define one or more of the following parameters:
   - You can define the **From Date/Time** and **To Date/Time** to filter only
     Snapshots that were created during that interval.
   - You can select the Origin of the Snapshot:
     - **All** – all Snapshots origins.
     - **User** – Snapshot created manually or via a Snapshot Policy which
       was attached to this Volume.
     - **Mirror** – Snapshots that were created by the Remote Mirroring
       application (using the Snapshot policy which was defined at the
       time of the Mirror creation).
     - **Object Storage** – Snapshots that were created by the Backup to
       Object Store (using the Snapshot policy that was defined at the
       time of the Backup definition).
   - **Snapshot Policy** – Select a Policy if you’d like to filter only
     Snapshots that were created by that specific Policy.