SnapVX time search overview
The TimeFinder SnapVX provides a highly efficient mechanism for obtaining periodic point copies of source data without the need for target equipment. The target devices only need to present point data to another host. By spreading the distribution over different levels, the space is used very efficiently. Only one delta snapshot is needed to write to the source volume to store raw data for multiple snapshots. If the source track is shared with one or more destinations, the source data is saved as an immediate delta when recording on that track and shared by all destinations. A letter to destination is only valid for a specific destination.
1. Take local copies (snapshots) of data at a specific point in time without needing to link source and target volumes – target volumes are only needed if host access to the data at a specific point in time is required.
2. Highly scalable – up to 256 snapshots per source volume Up to 1024 linked target volumes per source volume
3. High storage efficiency – Share tracks between different snapshots based on time.
TimeFinder SnapVX Terminology
Here is an explanation of the terms used in the SnapVX TimeFinder. Host postings to source volumes make delta snapshots in SRP. Snapshot deltas are the original data of the tracks that were changed after the snapshot was taken.
- Source volume – The VMAX3 device from which a copy should be recorded.
- Snapshot – An image of the source volume stored over time.
- Deltasnapshot – The traces of the original source volume at the time of the snapshot stored on the source volume during the host snapshot.
- Linked Target Volume is a VMAX3 device used to access data related to snapshots.
- Storage Resource Pool – A set of FAST-managed data pools that provide physical storage for VMAX3 thin devices.
When taking a snapshot, both the source device and the snapshot indicate the location of the data in the DRP. When the original number is recorded, the new recording is recorded asynchronously at the new location in the PRS. The original volume displays the new data. The snapshot always shows the location of the source data. The data stored at that moment becomes the delta of the snapshot. This is a mechanism to reroute the recording.
Under certain circumstances, SnapVX will use an asynchronous copy of the first plate (ACOFW). This can be done to avoid degrading the performance of the original device. Si z. B. The original song is assigned to the USB stick, it is best to copy it to a lower level and place the new recording on the USB stick.
Immediate generation and life
Each photo is assigned a generation number. If the name assigned to the snapshot is reused, the generation numbers are incremented. The last photo with the same name is marked with Generation 0, the previous Generation 1, and so on. If you give each photo a unique name, they will all be assigned to Generation 0. The output of the snapshot causes the generated numbers to be reallocated.
Time of Life (TTL) can be used to automatically stop recording at any given time. This setting can be made when taking or editing the picture later. The HYPERMAX control system executes the snapshot at the set time. If the photo has related objectives, it will not be completed. It is not complete until the last destination is released. The TTL can be specified as a specific date or as the number of days since its creation.
The snapshot must be linked to the target volume to access accurate hourly data from the host. The link can be in NoCopy or Copy mode. In copy mode, bound targets deliver copies of complete source volumes – as complete copy clones. In copy mode, attached targets always have a usable copy of the data after the snapshot – provided the copy is complete. By default, targets are created that are linked to the NoCopy mode. References in NoCopy mode are compact snapshots that use memory only for changed data stored in the SRP of the source device. Links in NoCopy mode do not store data on deletion. The shortcut mode can be changed after it has been created.
Recording to a paired target does not affect the images. The target can be linked to the snapshot to return to the original time. A snapshot can be associated with more than one objective. However, the target volume can only be associated with a single shot. Up to 1024 target volumes can be linked to one or more snapshots of a single source volume. This limitation can be achieved by linking the 1024 volumes to a single snapshot of the source volume, or by linking multiple target volumes to multiple snapshots of the same source volume.
There is no advantage for targets that are not copied in RPS mode and are different from the source RPS. When posting to the source volume, only delta snapshots are taken, which are stored in the RPS of the source volume. When writing, no copy operation is triggered to the target. The target volume, which is larger than the source, can be associated with the snapshot. This function is enabled by default. To avoid this, the SYMCLI_SNAPVX_LARGER_TGT environment variable can be set to DISABLE.
Linked objectives – defined/undefined pathways
Snap VX introduces the concept of defined state for linked target jobs. When a target is first assigned to a shot, all traces of it are considered undefined. Shortly after the connection, the background detection process changes the pointers of each track to display the position of the track at a given time. In an undefined state, the data location for the target must be resolved using snapshot pointers. In a given state, the target data points directly to the correct locations in the DRP.
The definition facilitates access to hosts on the target job that have not yet been copied to the target job by presenting the data directly from the PRS and eliminating the need to redirect to the source or a snapshot. The user does not have to wait for the target volume to be set to access the specified time. Writing to an undefined track activates the track detection process, and reading an undefined track is redirected to the correct track version at a specific point in time.
Switching and decoupling targets
Relink offers a convenient way to check the different snapshots and choose which one is accessible. For the relay operation there must be a connection between the snapshot of the source disk and the target. Reset can also be performed with different snapshots of the same source volume or with different generations of the same source volume. The Unlink operation removes the link between the image and the corresponding target. When the copy operation is finished, the destination references can be canceled in the copy mode. This creates a complete and independent copy of the source data on the target device.
Targets linked in NoCopy mode can be released at any time. After disconnecting the target device in NoCopy mode, the target device can no longer be considered usable. The destination had to share the tracks with the source volume and/or the delta recordings. These traces are no longer available on the target after a communication interruption, making it unusable.
Recovery to source
Because the source volume data changes from the host perspective, the source volume must be disconnected and then reinstalled before the recovery operation is performed. To recover from a linked target, a snapshot of the target must be taken; and this snapshot must be linked to that source. The source volume cannot be disconnected until copy processing is complete. Therefore, the link must be created in copy mode.
Recovery of snapshot
– Snapshots can be restored directly to the source volume.
– The data is reset to the time of the snapshot.
– From the delta interval difference work of the image, only the changed data needs to be retrieved.
Adjustment to related purpose
– Two-step process
1. Take a snapshot of the coupled target
2. Link this snapshot to the source volume (which will now be the linked target)
You can take pictures of related targets. These can then be linked to other objectives. It’s called the waterfall. There is no limit to the number of cascades that can be made as long as the overall limit for SnapVX is respected. However, given the effectiveness of the SnapVX technology, cascading is unlikely to be applied in practice. The label of the linked target does not affect the snapshot. It always remains intact – a golden copy, so to speak. If you need to experiment with the data on a linked target, you do not need to save the golden copy first. You can update the target data with the original recordings at any time by logging in when you have completed the experiment.
The linked target must be in a defined or copied state before a shot can be taken. A cascade record can only be restored to a paired target that is in copy mode and has been fully copied. When a paired target is in NoCopy mode, it cannot be deleted without first completing all the recordings made from it. A paired target that has a cascade snapshot must be fully copied before it is disconnected. A snapshot with linked targets cannot be interrupted.
time finder snapvx,cannot use the device for this function because it is a copy session source