First, it’s probably worth a quick definition of what snapshots are for those that thought I was talking about some tawdry pictures.

A definition offered by SNIA (Storage Networking Industry Association) says,”A fully usable copy of a defined collection of data that contains an image of the data as it appeared at the point in time at which the copy was initiated. A snapshot may be either a duplicate or a replicate of the data it represents.” In practical terms snapshots are a point-in-time copy of a dataset. In some cases it may be a read only copy and in others it may be completely writable. Generally, it is a way to have a local backup copy of data that doesn’t take up double the amount of space. More on how snapshots work and their inherent benefits another time though.

Over the past 5 years snapshot technology and usage has evolved tremendously. Snapshots can be used for more then just a quick and dirty backup mechanism. You can keep hourly, daily, weekly, and monthly snapshots of your data

The simplest way to leverage snapshots for another purpose is to create one as an interim backup to be used as the source of a backup to tape. The benefit of this is that snapshots only take a few seconds to create and then can be used as a static representation of the data for a backup that may take several hours. This means data can be changing on the live dataset even while the backup is running without concern for open files or data that is not in a consistent state.

The same benefit of having data in a static and consistent state can be leveraged for other uses as well:

To stage a replication or mirror – Same as staging for a backup with the same benefits of being able to access and modify the data right away.

To make data available for read only access – This may come in handy if you have an environment where you want to have software code writable by one group (the live data) and have another group accessing the last “known good” drop with read only access (the snapshot data).

To test new applications – If your snapshot deployment supports “writable” snapshots you can use them to test out upgrades to applications accessing the data without the worry of total data corruption to the real data.

Snapshots are much more then quick backups, so be creative! What other ways do you use snapshots? Snapshots can be a powerful tool. I’m interested to hear how others might use them.

Blog ya later!

Joe

This entry was posted on Friday, October 14th, 2005 and is filed under Storage Applications, Advisor - Joe. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.