TimeFinder Updates in PowerMaxOS 10
Thu, 18 Aug 2022 19:48:56 -0000
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The introduction of SnapVX in VMAX3 brought exciting changes in functionality and usability. Snapshots that do not require target volumes to capture a point-in-time, changed how users define snapshot schedules with new possibilities for efficiency and scalability. And in turn, those changes enabled more flexible use of copy volumes, referred to as linked targets.
The TimeFinder changes in PowerMaxOS 10, which runs on PowerMax 2500 and 8500 systems, are equally exciting. The knobs and controls have not changed from the previous version. The improvements are “in the sauce” so to speak, and have come directly from customer and field recommendations over the past few years.
Metadata efficiencies
The metadata for snapshots and deltas, Local Replication Cache, is dramatically more efficient. The internal structures are different from Replication Data Pointers (RDP) in previous PowerMax systems. But from the user perspective, monitoring is no different, with the same usage level and alerts.
Metadata usage for SnapVX linked targets and clones has also been dramatically improved, as it now scales proportionally to the changed data. Previously, the metadata allocation of a linked target or clone would reflect that of the source volume, regardless of changed data.
Target copy mode simplification
Nocopy mode for SnapVX has been considered best practice for several years now because it saves capacity and has proven to provide excellent performance. As such, the copy mode and nocopy mode options for clones and SnapVX linked targets have been removed. All clones and linked targets are space-efficient (nocopy mode) within an SRP. Storage efficiency has been a major focus across the industry for several years. Duplicating volume data within the system contradicts storage efficiency, especially if Data Reduction is enabled on target volumes, which is often the case.
Data will copy and duplicate only to targets that are in a separate Storage Resource Pool (SRP). We are not emphasizing the need for systems with multiple SRPs. Single SRP systems continue to be considered best practice because this configuration provides for optimal performance. Use snaps and clones for logical protection, and use SRDF remote replication for physical protection.
Precopy mode has also been removed because it is a function of copy mode. And the architectural changes since VMAX3 have eliminated the need for precopy mode. The challenges precopy was designed to address no longer exist, so it has been deprecated in PowerMaxOS 10.
Target volume performance
When a target is linked to a SnapVX snapshot, an internal process sets the pointers on the target volume to point to the data. In previous releases, this process is called the define scan. A flag on each link reports when the target has been fully defined.
New and quicker internal functions replace the define scan in PowerMaxOS 10. The define flag is still used to monitor this process, so users can continue to use existing commands and scripts to monitor when the internal operations are complete.
Clones and linked targets also report “copied” when the internal process has completed, regardless of SRP location. Whether data is copied or is only defined, users have a single method to monitor copy states.
Space-efficient snapshot restores
In PowerMaxOS 10, snapshot restores swap pointers to increase the speed of a restore, as compared to previous releases in which data would be copied back to the source volumes.
Deprecation of VP Snap and Mirror
The original TimeFinder option, TF/Mirror, is finally going away. It is a bittersweet move because it was a key building block to where TimeFinder is today. But, other than compatibility with legacy scripts, Mirror has provided no advantages over other TimeFinder options for years.
Business Continuance Volumes (BCVs) remain an option. Using BCVs for clones or SnapVX linked targets may help to identify your copy volumes and report on their capacity without affecting feature functionality.
VP Snap is being deprecated, but it may be more accurate to say that the efficiencies of VP Snap have been applied to Clone. There is no longer a need for VP Snap, and so the command set has been removed
Other clone improvements
Clones have increased from 16 to 256 clones per source volume, and support storage group operations.
Resources
Author: Michael Bresnahan, Technical Marketing Engineer