DiskShadow Interactions with DataCore SANsymphony
This topic provides usage notes, as necessary, to explain the effects certain DiskShadow commands have on virtual disks. DiskShadow commands that do not affect virtual disks are not documented.
Examples and instructions provided use DiskShadow commands as a point of reference. If using a different VSS requester, please adapt the instructions. See the DataCore SANsymphony Help for instructions on performing snapshot operations if necessary.
VSS Hardware Provider supports shadow copies that were created with VSS Hardware Provider only. VSS Hardware Provider does not support pre-existing snapshots on DataCore Servers. A shadow copy set may contain one or more virtual disks. A snapshot will be created for each virtual disk.
DiskShadow Commands
Add Volume
Adds a volume (created from a virtual disk) to the shadow copy set.
Break
When the break command is issued for a shadow copy set, differential snapshots will be promoted to full, and then all associated snapshots will be split.
The snapshots become read/writable and the shadow copy set is no longer under the control of shadow copy management.
After the break command is issued, the resulting virtual disk name may exceed the size limit to allow for creation of shadow copies. Rename the virtual disk if it may be used as the source of a shadow copy. Source virtual disk names should not exceed 41 characters.
Create
When the create command is issued, a snapshot will be created on the DataCore Server with the active path. Snapshots will be created from the preferred snapshot pool, if assigned.
DataCore recommends that a preferred snapshot pool be set for virtual disks used to create snapshots. If the preferred snapshot pool is not set, then the snapshot will be created from the first available pool found.
The snapshot type will be differential (logical copy) by default; to create a full snapshot, set the plex option.
One snapshot will be created for each volume (virtual disk) in the shadow copy set.
The shadow copy set is automatically imported to the VSS client that created it unless the transportable option is set.
The snapshot will be read-only until the break command is issued.
If the shadow copy source is the source of a replication, a checkpoint marker will be sent to the replication destination to update the assigned checkpoint snapshot. The snapshot to update should be pre-configured on the destination server in order to act upon it. (The snapshot created on the replication destination is not part of the shadow copy.)
The source virtual disk name should not exceed 41 characters.
If Continuous Data Protection (CDP) is enabled on the source virtual disk, an expiring rollback will be created from the source.
Checkpoint marker configuration must be performed in DataCore SANsymphony. See Replication Operations in the DataCore SANsymphony Help for important checkpoint information.
Delete shadows
When the delete shadows command is issued, the associated snapshots are also deleted on the DataCore Server.
Import
The import command gives control of the shadow copy set (snapshot) to the requesting VSS client. The snapshot is served from the DataCore Server to the VSS client.
Before importing the shadow copy set, the metadata file should be loaded to the VSS client where the shadow copy set will be imported.
Shadow copy sets can be imported to any VSS client supported by the DataCore Server. The VSS Hardware Provider software must be installed on any machine that the shadow copy will be imported to. An Ethernet connection and either an iSCSI or Fibre Channel connection must exist between the VSS client and the DataCore Server.
Mask
When the mask command is issued, the volumes (virtual disks) in the shadow copy set will be unserved from the VSS client.
Resync
When the resync command is issued, a revert from snapshot command is performed on the associated snapshots.
Set context
The persistent parameter is supported. VSS shadow copies are not persistent by default.
Always set the persistent parameter.
Set Option
The following parameters are supported:
- plex - creates a full snapshot type.
- differential - creates a differential snapshot type. (This is the default snapshot type when a shadow copy is created.)
- transportable - the shadow copy is not imported or exposed to the VSS client that created it.