A CVD snapshot is a centrally retained point-in-time image of CVD content, including OS, applications and user data, that enables complete restoration of a specific endpoint or a specific file. The Mirage server generates snapshots and keeps generations of snapshots available according to a retention policy.
Automatic Snapshot Generation
After the first successful CVD upload to a device, the Mirage server attempts to synchronize with the device at regular intervals, and to create a CVD snapshot when the synchronization is successful. The frequency of the attempts is defined by the Upload Change Interval parameter, for example every 60 minutes. See Working with Upload Policies.
The success of a synchronization, and the snapshot creation, depends on the server being able to access the device at the scheduled intervals. This is not always possible since the device might be closed or the Snooze feature might be in effect. See Suspend and Reactivate Synchronization.
Snapshots can also be generated independently of the Upload Change Interval timing, in the following cases:
Before a base layer update. This allows an administrator to revert to the CVD state before the update if the update fails or is problematic, or after any migration.
Before reverting to a snapshot. This keeps the current endpoint state available in case a rollback is required.
Whenever the administrator performs a forced upload. See Reconnect a Device to a CVD.
According to these circumstances, the interval between specific snapshots can be longer or shorter than the time defined by the Upload Change Interval parameter.
Snapshot Retention Policy
The system keeps historical snapshots according to a retention policy, and can be used to restore files on the device.
You define the snapshot retention in the Snapshots kept area of the System Configuration General tab. See General System Settings. The system keeps a maximum number of CVD snapshots at hourly, daily, weekly, and monthly intervals.
Retention category |
Description |
|---|---|
Number of snapshots at 1 hour intervals |
Number of consecutively generated snapshots that the system keeps. For example, the value 8 means that the system always keeps the latest 8 successful CVD snapshots in this category. Historical snapshots older than the latest 8 are discarded. However, if daily snapshot retention is defined, whenever a first snapshot of a new day is created, the oldest snapshot in the Hourly category becomes a candidate as the newest daily snapshot. The default number of Hourly snapshots is zero, meaning new snapshots are not kept as they are created. You can change this value. |
Number of snapshots at 1 day intervals |
Number of snapshots that the system keeps in the Daily category. For example, the value 7, the default, means that the system always keeps the earliest-created snapshot in each new calendar day, up to 7 snapshots in this category. If hourly snapshots are defined, the oldest snapshot in the hourly category becomes the newest daily snapshot. Historical snapshots older than the latest 7 in the daily category are discarded. However, if weekly snapshot retention is defined, whenever a first snapshot of a new week is created, the oldest daily snapshot becomes the newest weekly snapshot. |
Number of snapshots at 1 week intervals |
Number of snapshots that the system keeps in the Weekly category. For example, the value 3, the default, means that the system always keeps the earliest-created snapshot in each new calendar week, up to 3 snapshots in this category. Other aspects of the weekly snapshot retention follow the same pattern as daily snapshot retention. |
Number of snapshots at 1 month intervals |
Number of snapshots that the system keeps in the Monthly category. For example, the value 11, the default, means that the system always keeps the earliest-created snapshot in each new calendar month, up to 11 snapshots in this category. Other aspects of the monthly snapshot retention follow the same pattern as daily or weekly snapshot retention. |
The intervals between snapshots retained in each category depend on the factors described in Automatic Snapshot Generation, and how device availability affects the retention rollover timing. For this reason, the snapshots in the daily, weekly, and monthly retention categories can typically have time intervals of at least a day, week, or month between them.
Automatic snapshots taken before a base layer update, before reverting to a snapshot, or forced uploads are counted against the snapshot retention capacity. They cause the number of regular snapshots retained to decrease.
