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Automatic Snapshot Creation and Retention
139
CloudPlatform supports snapshots of disk volumes. Snapshots are a point-in-time capture of virtual
machine disks. Memory and CPU states are not captured. If you are using the Oracle VM hypervisor,
you can not take snapshots, since OVM does not support them.
Snapshots may be taken for volumes, including both root and data disks (except when the Oracle
VM hypervisor is used, which does not support snapshots). The administrator places a limit on the
number of stored snapshots per user. Users can create new volumes from the snapshot for recovery
of particular files and they can create templates from snapshots to boot from a restored disk.
Users can create snapshots manually or by setting up automatic recurring snapshot policies. Users
can also create disk volumes from snapshots, which may be attached to a VM like any other disk
volume. Snapshots of both root disks and data disks are supported. However, CloudPlatform does not
currently support booting a VM from a recovered root disk. A disk recovered from snapshot of a root
disk is treated as a regular data disk; the data on recovered disk can be accessed by attaching the
disk to a VM.
A completed snapshot is copied from primary storage to secondary storage, where it is stored until
deleted or purged by newer snapshot.
14.5.1. Automatic Snapshot Creation and Retention
(Supported for the following hypervisors: XenServer, VMware vSphere, and KVM)
Users can set up a recurring snapshot policy to automatically create multiple snapshots of a disk
at regular intervals. Snapshots can be created on an hourly, daily, weekly, or monthly interval. One
snapshot policy can be set up per disk volume. For example, a user can set up a daily snapshot at
02:30.
With each snapshot schedule, users can also specify the number of scheduled snapshots to be
retained. Older snapshots that exceed the retention limit are automatically deleted. This user-defined
limit must be equal to or lower than the global limit set by the CloudPlatform administrator. See
Section 15.2.1, “Globally Configured Limits”. The limit applies only to those snapshots that are taken
as part of an automatic recurring snapshot policy. Additional manual snapshots can be created and
retained.
14.5.2. Incremental Snapshots and Backup
Snapshots are created on primary storage where a disk resides. After a snapshot is created, it is
immediately backed up to secondary storage and removed from primary storage for optimal utilization
of space on primary storage.
CloudPlatform does incremental backups for some hypervisors. When incremental backups are
supported, every N backup is a full backup.
VMware vSphere Citrix XenServer KVM
Support incremental
backup
N Y N
14.5.3. Volume Status
When a snapshot operation is triggered by means of a recurring snapshot policy, a snapshot is
skipped if a volume has remained inactive since its last snapshot was taken. A volume is considered
to be inactive if it is either detached or attached to a VM that is not running. CloudPlatform ensures
that at least one snapshot is taken since the volume last became inactive.