Snapshots

This page allows you to take, remove, and edit snapshots, as well as to configure snapshot schedule and retention settings.

Snapshots minimize disk consumption by preserving individual blocks rather than the whole files. Extra space may be consumed when files are updated or removed.

To take a snapshot for an iSCSI LUN:

1. Select the iSCSI LUN of which you wish to take a snapshot.
   Note: You can press and hold Ctrl or Shift to select multiple items.
2. Click Snapshot > Take a Snapshot.
3. Enter the description in Description for the snapshot to be taken.
4. Tick or untick the Lock checkbox to determine whether the snapshot will ignore the retention settings when automatic removal is to be triggered.
5. Click OK to start taking a snapshot.

To remove a snapshot of an iSCSI LUN:

1. Select an iSCSI LUN you wish to remove the snapshots of.
2. Click Snapshot > Snapshot List.
3. Select one or more snapshots you wish to remove, and click Remove.
   Note: You can press and hold Ctrl or Shift to select multiple items.
4. You will see a confirmation message. Click Delete to confirm the removal.

To edit a snapshot of an iSCSI LUN:

1. Select an iSCSI LUN you wish to edit the snapshots of.
2. Click Snapshot > Snapshot List.
3. Select a snapshot you wish to edit, and click Edit.
4. You can do any of the following to edit the snapshot:
   • Change the description of the snapshot in Description.
   • Tick or untick the Lock checkbox to determine whether the snapshot will ignore the retention settings when automatic removal is to be triggered.
5. Click OK to save your settings.

To configure scheduled snapshots:

With scheduled snapshots, Snapshot Replication will automatically take snapshots at the pre-determined time and frequency, and it will thus lighten your workload to take snapshot manually.

1. Select an iSCSI LUN.
   Note: You can press and hold Ctrl or Shift to select multiple items.
2. Click Settings.
3. In the Schedule tab, tick the Enable snapshot schedule checkbox, and set up the time and frequency to take snapshots. To cancel scheduled snapshots for this LUN, please untick the checkbox.
4. Click OK to save your settings.

To configure the retention settings for the scheduled snapshots:

1. Select an iSCSI LUN.
   Note: You can press and hold Ctrl or Shift to select multiple items.
2. Click Settings.
3. Select Retention tab.
4. Specify how to retain and delete snapshots.
   • Choose between these three options:
     • Always retain snapshots: When the maximum number of snapshots is reached, Snapshot Replication will stop taking new snapshots without removing the ones already taken.
     • Retain [number] latest snapshots: When the maximum number of snapshots is reached, the oldest snapshots will be overwritten by newly taken ones.
       Note: The number is subject to be different according to your Synology product model.
     • Advanced retention rules: You can configure retention rules for specified time ranges. Click Configure to edit the retention rule. For more information, please refer to the Retention Policy note.
   • Choose when to delete snapshots: You can choose when to delete snapshots. We suggest setting the time to off-peak hours to reduce server load.
     • Set the time to a specific time of day, such as 08:00 or 15:00.
     • While taking snapshots: The old snapshots will be deleted when new snapshots are taken.
5. Click OK to save your settings.

To configure the consistent state of your iSCSI LUN snapshots:

1. Select an iSCSI LUN.
   Note: You can press and hold Ctrl or Shift to select multiple items.
2. Click Settings.
3. Select the Application tab.
4. Tick/untick Enable application-consistent snapshots checkbox to switch between the following consistent states:
   • Application consistent: This type of snapshot can only be taken when Synology Storage Console is installed on your Windows server or VMware vCenter Server depending on your operating environment to communicate with DSM UC. When application-consistent snapshots are triggered on DSM, applications will be notified and flush all the data from memory to the LUN on which the snapshot is taken to guarantee data consistency.
     Note: If Synology Storage Console has not been installed in your operating environment, the application-consistent snapshot will remain disabled even if the checkbox is ticked.
   • Crash consistent: If no Synology Storage Console is installed on either of your clients, you can only capture crash-consistent snapshots of LUNs. When they are triggered, applications will not be notified to flush the data from memory to the LUN and therefore guarantee no data consistency.
5. Click OK to save your settings.

____

Retention Policy

This option provides an ideal solution to help you specify the maximum amounts of snapshot versions to save your volume space, but you may need to retain your snapshots for longer periods of time. There are a few things to note about Retention Policy:

• Synology employs the GFS, or Grandfather-Father-Son retention policy. You can configure the maximum amounts of snapshot versions to be retained for the following time ranges respectively: hourly, daily, weekly, monthly, and yearly.
• One snapshot can meet several retention rules at the same time. For example, one snapshot can meet the daily, weekly, and monthly rules.
• The earliest snapshots will be retained if you take many snapshots within a certain period. For example, if you set a 10 weekly snapshots retention rule, and your snapshot schedule is set to take 1 snapshot a day, Snapshot Replication will retain the earliest snapshot of each week for the past 10 weeks.
• If you have not taken snapshots for a certain period, the system will retain the most recent snapshots. For example, if the daily snapshot rule is set as 15 and there were not any snapshots taken in the past 30 days, the system will retain the snapshots taken 30 to 45 days ago.
• All snapshot versions within one hour since the taking of newest snapshot will be kept by default, for your convenience to find and restore from recent snapshot versions. You can also lock a snapshot to prevent it from automatic removal by your retention rules.

Example 1:
If you want to keep daily snapshots for the past 3 months, weekly snapshots for the past 4 to 6 months, and monthly snapshots for the past 7 to 9 months, you need to input 0 for hourly snapshots, 90 for daily snapshots, 24 for weekly snapshots, 9 for monthly snapshots, and 0 for yearly snapshots.

Example 2:
If you want to keep hourly snapshots for the past 2 days, daily snapshots for the past week, weekly snapshots for the past month, and monthly snapshots for the past year, you need to input 48 for hourly snapshots, 7 for daily snapshots, 4 for weekly snapshots, 12 for monthly snapshots, and 0 for yearly snapshots.