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:
- 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.
- Click Snapshot > Take a Snapshot.
- Enter the description in Description for the snapshot to be taken.
- Tick or untick the Lock checkbox to determine whether the snapshot will ignore the retention settings when automatic removal is to be triggered.
- Click OK to start taking a snapshot.
To remove a snapshot of an iSCSI LUN:
- Select an iSCSI LUN you wish to remove the snapshots of.
- Click Snapshot > Snapshot List.
- 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.
- You will see a confirmation message. Click Delete to confirm the removal.
Note:
- If an iSCSI LUN is replicated, its latest snapshot synced to the destination server will be preserved and cannot be removed.
- For better replication performance, several snapshots of the iSCSI LUN will be prevented from removal during the sync.
To edit a snapshot of an iSCSI LUN:
- Select an iSCSI LUN you wish to edit the snapshots of.
- Click Snapshot > Snapshot List.
- Select a snapshot you wish to edit, and click Edit.
- 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.
- Click OK to save your settings.
Note:
- You cannot take snapshots of iSCSI LUNs when a volume has less than 1 GB of free space.
- In Snapshot Replication on your Synology Unified Controller, you cannot take, edit or remove the snapshots of any iSCSI LUNs used by Cinder. For more information, please refer to Synology Unified Controller Help > iSCSI Manager > LUN.
- If your iSCSI LUNs are used in any established iSCSI sessions on Windows Server/VMware ESXi Server, you are recommended to install the Synology Snapshot Manager plug-in to avoid the risk of data inconsistency. Otherwise, you must stop all related applications and log out of all iSCSI sessions before proceeding with editing the snapshot.
- Upon completion of taking a snapshot or creating a replication task, if the status turns out to be Abnormal/Crashed, please delete the snapshot/replication and try again.
- When you restore an iSCSI LUN to a snapshot version, you will lose all changes made to this iSCSI LUN after the time point when the snapshot was taken.
- If the status of an iSCSI LUN changes to Unavailable, it means that some data-related errors occurred when the iSCSI LUN is accessed. The iSCSI LUN will be temporarily inaccessible to avoid severe data loss. Please contact Synology for support as soon as possible.
Synology Snapshot Manager
Synology Snapshot Manager is a plug-in allowing you to take application-consistent snapshots directly from DSM UC. After installing and activating Synology Snapshot Manager on Windows Server or VMware ESXi Server, you can click Snapshot Manager Registration List to see the registered clients.
- In the VMware environment, you need to install Synology Snapshot Manager on the Windows server where VMware vCenter Server has been installed. When a snapshot taking is triggered on DSM UC, VMware vCenter Server will be notified and flush all the data from memory to the LUN on which the snapshot is taken to guarantee data consistency. Once the snapshot is complete, VMware vCenter Server will resume normal I/O operations of VMware datastore. Synology Snapshot Manager for VMware vCenter Server is supported on vSphere 5.1 and above.
- In the Windows environment, you need to install Synology Snapshot Manager on your Windows server. When a snapshot taking is triggered on DSM UC, Synology Snapshot Manager will leverage Microsoft Volume Shadow Copy Service (VSS) technology to generate consistent point-in-time copies of your data. Synology Snapshot Manager for Windows is supported on Windows Server 2008 R2, 2012, and 2012 R2.
- Synology Snapshot Manager can be downloaded for free from www.synology.com.
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.
- Select an iSCSI LUN.
Note: You can press and hold Ctrl or Shift to select multiple items.
- Click Settings.
- 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.
- Click OK to save your settings.
To configure the retention settings for the scheduled snapshots:
- Select an iSCSI LUN.
Note: You can press and hold Ctrl or Shift to select multiple items.
- Click Settings.
- Select Retention tab.
- 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.
- Click OK to save your settings.
Note:
An iSCSI LUN can take up to 255 snapshots. It is suggested to activate snapshot retention policy to ensure scheduled snapshot tasks run smoothly.
To configure the consistent state of your iSCSI LUN snapshots:
- Select an iSCSI LUN.
Note: You can press and hold Ctrl or Shift to select multiple items.
- Click Settings.
- Select the Application tab.
- Tick/untick Enable application-consistent snapshots checkbox to switch between the following consistent states:
- Application consistent: Snapshots in this consistent state can be taken only when Synology Snapshot Manager 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 UC, applications will be notified, and flush all the data from memory to the LUNs to be taken a snapshot of, hence the assurance of data consistency.
Note: If Synology Snapshot Manager has not been installed on your operating environment, the application-consistent snapshot will remain disabled even if the checkbox is ticked.
- Crash consistent: If Synology Snapshot Manager has not been installed on any of your clients, you can only capture crash-consistent snapshots of LUNs. When crash-consistent snapshots are triggered, applications will not be notified to flush the data from memory to the LUNs, hence the inability to guarantee data consistency.
- Click OK to save your settings.
Note:
- Changing the consistent state settings will affect the equivalent settings in the Replication page.
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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.
