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When does storage snapshot technology work best?
Snapshots do not replace backup, but they can be used to enhance a data protection strategy if you use them at the right time and for the right tasks.
There are many use cases for storage snapshot technology. But the most important thing to remember is that while many backup applications leverage snapshots as a way of enabling features such as instant recovery, a snapshot is not a standalone backup replacement.
Storage snapshot advantages
Snapshots are best suited to the task of virtual machine rollbacks for infrastructure servers or offline application servers. This might sound a lot like a point-in-time recovery, but the processes are quite different, as are the implications of using storage snapshots versus performing a standard recovery.
A snapshot does not create a copy of your data; instead, it results in the creation of a differencing disk. This differencing disk has a parent-child relationship to the original data source and intercepts all future write operations. This leaves the original data source in an untouched state. Performing a point-in-time recovery using snapshot technology involves removing one or more differencing disks so the system can be returned to a previous state. This is in sharp contrast to a traditional data restoration that handles point-in-time recovery by copying data from a backup.
Brien Posey explains how storage snapshotswork and where the technology might fit in a
data protection strategy.
A storage snapshot's reliance on differencing disks makes snapshots well-suited for some types of rollbacks, but not others. For example, if you wanted to protect yourself prior to applying a service pack to an infrastructure server, snapshots would be an ideal way to do this. The snapshot can be created instantly, and without taking the system offline. If something were to go wrong during the service pack installation process, the system could be reverted to a previous state by applying snapshot technology.
Storage snapshot drawbacks
Conversely, snapshot technology is often a poor choice for protecting application servers unless a snapshot is made while the server -- typically a virtual machine -- is offline. Storage snapshots preserve the state of the server's storage as it existed at a particular point in time, but many snapshot offerings do not capture memory state, which is critical to an application server. Finally, most storage snapshot products are not application-aware, although the Hyper-V 2016 checkpoint feature (the snapshot mechanism for Hyper-V) will include application awareness.
