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The following are explanations of terms that are commonly used throughout the paper:
Storage Resource Pool (SRP): A collection of data pools which provide physical storage for thin devices. SRPs are managed by Fully Automated Storage Tiering (FAST).
Source Volume: A LUN that has SnapVX snapshots from it, either with or without linked targets.
Snapshot: A preserved point-in-time image of a source volume. A snapshot uses pointers in cache to indicate which version of a track is applicable to the specific point-in-time; either a track that resides on the source volume, or a snapshot delta.
Snapshot Delta: A point-in-time version of a source volume track that was preserved during a host write to a source volume that had an active snapshot.
Linked Target Volume: A LUN that is linked to a SnapVX snapshot to make the point-in-time of the snapshot accessible to a host. Linked targets have two modes:
Note: See Appendix D: Nocopy Linked Target behavior before HYPERMAX OS 5977.810.184 for changes to the nocopy target functionality introduced in HYPERMAX OS 5977.810.184.
The type of copy mode does not affect how much data needs to be updated on the target. Whether in copy mode or nocopy mode, a link operation causes a full update to the target, and a relink operation causes a differential update to the target.
The table below shows that it is the existence of a current relationship between any snapshot of the source and the target volume that determines if the target update is full or differential regardless of the copy mode.
|
Link |
Relink |
Copy mode |
Full target update |
Differential target update |
Nocopy mode |
Full target update |
Differential target update |
Link and Relink: Operations to update the data on target volume with the point-in-time image of a snapshot.
Unisphere: Unisphere is an HTML5 web-based application that allows you to configure and manage PowerMax, VMAX All Flash, and VMAX storage systems. The term Unisphere incorporates "Unisphere for PowerMax" for the management of PowerMax and All Flash storage systems running PowerMaxOS 5978, and "Unisphere for VMAX" for the management of VMAX All Flash and VMAX storage systems running HYPERMAX OS 5977 and Enginuity OS 5876.