Storage Array Snapshots

In today’s data center industry there is a misconception about the storage snapshot as a Backup. The main one is storage snapshots are not backup, they are just point-in-time copies. It’s unclear from where the idea came from.

Backup is a collection of data stored on (usually removable) non-volatile storage media for purposes of recovery in case the original copy of data is lost or becomes inaccessible; also called a backup copy. To be useful for recovery, a backup must be made by copying the source data image when it is in a consistent state.

– The SNIA ( Storage Networking Industry Association) defines

In data centers, we purchase Storage Array-like NetApp, Dell EMC, WD IntelliFlash, HP3PAR, most of the storage vendors have a powerful snapshotting system ( we pay for it ) but mostly we use the powerful storage arrays as dumb disks. We can use the powerful snapshot and replication capabilities of the Storage arrays for the Backup.

A storage snapshot does not consume any space by default when it is created. A storage snapshot is a set of reference markers for data at a particular point in time. A snapshot acts like a detailed table of contents, providing the user with accessible copies of data that they can roll back to. It is just a copy of the metadata that holds information about the data snapped.

Storage snapshots are created instantly, which means they are done within seconds. So you can have the RPOs down to less than a minute. Best approach of Backup is to use the storage snapshots to lower the RPO and RTO to minutes instead of Hours / days ( read more about RPO and RTO here )

The array’s replication capabilities move the snapshot copies to the secondary site / DR Site

Consistency of the Snapshots

One of main parts in the SNIA definition is backup data must be in the consistent state,

Applications like database servers typically write to log files before it writes to the database, it is important that the contents in the memory and pending writes have to be flushed to the filesystem (disk) when we trigger a backup

In the vSphere environment, the consistency can be achieved by calling the VM snapshot with the Quiesce flag, VMware Tools is used to quiesce the file system in the virtual machine. Quiescing a file system is a process of bringing the on-disk data of a physical or virtual computer into a state suitable for backups. This process might include such operations as flushing dirty buffers from the operating system’s in-memory cache to disk, or other higher-level application-specific tasks.

Quiescing indicates pausing or altering the state of running processes on a computer, particularly those that might modify information stored on disk during a backup, to guarantee a consistent and usable backup.

Nimesa leverages the storage snapshot and clone capabilities of the array to create an application-aware and consistent backup, Nimesa’s integration with multiple storage vendors ensures the operating system and the application running on vSphere virtual machine are on consistent state before the snapshot is created.

Storage snapshot enables the implementation of data-protection with lower RPO and RTO, Array replication capabilities will make sure your data is written on the secondary site and available to recover through Nimesa during a disaster.

You can read more about the Copy data management with your Inplace Storage here

Also published on Medium.

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