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accessible snapshots, while it maintains 512 non-client-accessible snapshots. If the
maximum number of snapshots exists and another one is taken, the oldest snapshot is
deleted to make room for the new one.
Another example is that Double-Take snapshots must be created within one minute
because Volume Shadow Copy snapshots must be created within one minute. If it takes
longer than one minute to create the snapshot, the snapshot will be considered a failure.
Additionally, Volume Shadow Copy will not revert snapshots of a volume with operating
system files, therefore Double-Take is also unable to revert a volume with operating system
files.
You must also keep in mind that if you are using extended functionality provided by Volume
Shadow Copy, you need to be aware of the impacts that functionality may have on DoubleTake. For example, if you change the location where the shadow copies are stored and an
error occurs, it may appear to be a Double-Take error when it is in fact a Volume Shadow
Copy error. Be sure and review any events created by the VolSnap driver and check your
Volume Shadow Copy documentation for details.
Other snapshot functionality—You can use Volume Shadow Copy for other uses
outside Double-Take, for example Microsoft Backup uses it. Keep in mind though that the
driver for Volume Shadow Copy is started before the driver for Double-Take. Therefore, if
you use snapshots on your source and you revert any files on the source that are protected
by your job, Double-Take will not be aware of the revert and the file change will not be
replicated to the target. The file change will be mirrored to the target during the next
mirroring process.
NAT—Agentless Hyper-V jobs do not support NAT environments.
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Live migration—Windows 2012 live migration is supported for CSV clustered virtual machines,
but the shared-nothing configuration is not supported. If a virtual machine is migrated, DoubleTake will automatically start a remirror.
Supported configurations—The following tables identify the supported configurations for an
agentless Hyper-V job.
Configuration
Description
Supported
One to one
active/standby
You can protect virtual machines on an active
host to a standby host. The standby host has no
active virtual machines, only the replica virtual
machines. Replication will occur in only one
direction.
X
One to one
active/active
You can protect virtual machines on an active
host to another active host. Each host has
active virtual machines in addition to replica
virtual machines. Replication will be bidirectional between the hosts.
X
Chapter 2 Agentless Hyper-V requirements
Not
Supported
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