The SAN Volume Controller FlashCopy® feature transfers a point-in-time copy of a source virtual disk (VDisk) onto a designated target VDisk. You must create or already have an existing target VDisk before you can transfer the copy. You must also ensure the target VDisk has enough space available to support the amount of data that is being transferred.
After the mapping is started, all of the data that is stored on the source VDisk can be accessed through the target VDisk. This includes any operating system control information, application data, and metadata that was stored on the source VDisk. Because of this, some operating systems do not allow a source VDisk and a target VDisk to be addressable on the same host.
In order to ensure the integrity of the copy that is made, it is necessary to completely flush the host cache of any outstanding reads or writes before you proceed with the FlashCopy operation. You can flush the host cache by unmounting the source VDisks from the source host before you start the FlashCopy operation.
Because the target VDisks are overwritten with a complete image of the source VDisks, it is important that any data held on the host operating system (or application) caches for the target VDisks is discarded before the FlashCopy mappings are started. The easiest way to ensure that no data is held in these caches is to unmount the target VDisks prior to starting the FlashCopy operation.
Some operating systems and applications provide facilities to stop I/O operations and to ensure that all data is flushed from caches on the host. If these facilities are available, they can be used to prepare and start a FlashCopy operation. See your host and application documentation for details.
Some operating systems are unable to use a copy of a VDisk without synthesis. Synthesis performs a transformation of the operating system metadata on the target VDisk to allow the operating system to use the disk. See your host documentation on how to detect and mount the copied VDisks.