SnapVX and Local Replication Operations
SnapVX is the local replication method on PowerMax. The exam expects you to know that a snapshot is pointer-based and needs no target, that a target only exists once you link, and that restore is destructive to the source.
Concepts
- A snapshot is created on a source device or storage group. It is space-efficient: only changed tracks are tracked, and that space comes from the SRP's snapshot capacity as the source changes.
- Each source device can hold up to 1,024 SnapVX snapshots; names are unique per source or storage group so scripts and policies can find them.
- A snapshot can exist with no target at all. Linking creates a target device that exposes the point-in-time image; the target must be at least as large as the source and can sit in a different storage group.
- Snapshot policies attach to storage groups and take snapshots on a schedule; these provide routine recovery points without manual work.
Operations
- Create: symsnapvx -sid -sg -name create.
- Link: symsnapvx -sid -sg -name -lnk -target link.
- Restore: writes the snapshot image back onto the source, overwriting current data, so confirm intent before running it.
- Terminate: symsnapvx -sid -sg -name terminate; linked targets go with it.
Worked example
A test team needs a copy of production at 02:00. Create a snapshot of the production storage group at 02:00 (or let a policy do it), then link it to a pre-existing target storage group. The target is presented to test hosts through its own masking view. After testing, terminate the snapshot and remove the link; production was never touched. If testing corrupts the target, link a fresh snapshot rather than restoring anything.
Traps
Believing a target must exist before a snapshot can be taken; running restore when a link was intended; ignoring SRP snapshot capacity, which grows as sources change; and terminating a snapshot while a backup host still reads the linked target.