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Deep dive in Snapshot & SnapManager Tool

Could someone provide detailed answer for below questions. I belive this will help to understand the snapshots better.

  1. Does Data ONTAP freezes the I/O while creating snapshot of volume on the storage system? If yes, where does the incoming data lying/stored during the freeze period.
  2. How the SnapManager Tool works? Why do we need snapmanager tool to create consistent snapshot copy of a volume which hosts LUNs to the server?
  3. Why the snapshot scheduled & created on storage system is not consistent for volumes which hosts LUNs to severs?
  4. Why do we have limit for number of snapshots (255) for any volume?

Re: Deep dive in Snapshot & SnapManager Tool

1. Snapshot is simply CP that was not removed. So when snapshot is created, additional CP is triggered. From now on it is not different from regular write path.

2,3. Snapshots are crash consistent. Some applications can do better and create application consistent snapshots. That's what various snap managers do.

4. Because it was implemented this way?