1. Usefull Link
2. Overview
SnapSure is a VNX for File feature that saves disk space and time by creating a point-in-time view of a file system. This logical view is called a checkpoint and can be mounted as a read-only file system. SnapSure is mainly used by low-activity, read-only applications such as backups and file system restores.
SnapSure is not a discrete copy product and does not maintain a mirror relationship between source and target volumes. It maintains pointers to track changes to the primary file system and reads data from either the primary file system or from a specified copy area. The copy area is referred to as a SavVol, and is defined as a VNX for File metavolume.
SnapSure is not a discrete copy product and does not maintain a mirror relationship between source and target volumes. It maintains pointers to track changes to the primary file system and reads data from either the primary file system or from a specified copy area. The copy area is referred to as a SavVol, and is defined as a VNX for File metavolume.
SnapSure checkpoints provide users with multiple point-in-time views of their data. In the illustration above the user’s live, production data is a business proposal Microsoft Word document. If they need to access what that file looked like on previous days, they can easily access read-only versions of that file as viewed from different times. This can be useful for restoring lost files or simply for checking what the data looked like previously. In this example, checkpoints were taken on each day of the week
PFS
- A production file system, or PFS, is any typical VNX file system that is being used by an application or user.
Checkpoint
- A point-in-time view of the PFS. SnapSure uses a combination of live PFS data and saved data to display what the file system looked like at a particular point-in-time. A checkpoint is thus dependent on the PFS and is not a disaster recovery solution. Checkpoints are also known as snapshots.
SavVol
- Each PFS with a checkpoint has an associated save volume, or SavVol. The first change made to each PFS data block triggers SnapSure to copy that data block to the SavVol.
Bitmap
- SnapSure maintains a bitmap of every data block in the PFS where it identifies if the data block has changed. Each PFS with a checkpoint has one bitmap that always refer to the most recent checkpoint.
Blockmap
- A blockmap of the SavVol is maintained to record the address in the SavVol of each saved data block. Each checkpoint has its own blockmap.
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