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Storage Area Networks For Dummies® by Alex Nikitin, Christopher Poelker

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Chapter 10. Mirror, Mirror: Point-in-Time Copies

A Point-in-Time (PiT) copy is exactly what its name says: a copy of your data at a particular point in time. To best understand what this means, look at yourself in the mirror and make some funny faces; everything that you do is reflected back instantly as a perfect copy. Well, maybe not perfect, but....

Now get a digital camera ready, make a face, and snap a picture of the mirror. Print the picture and tape it to the mirror over your reflected image. The picture is of you at the exact moment you snapped the picture, but your face has continued to change expressions (such as the frustrated look of trying to find the lost end to the roll of tape). The printed image is a Point-in-Time copy of the real thing ... possibly your good side, too.

Translating this concept into computer-speak, you can make a perfect copy of your application's data, frozen in time. Now what do you do with this copy?

This chapter guides you through the basics of Point-in-Time copy technology, which allows you to use your SAN (storage area network) to create duplicate copies of your data — which can then be used for alternate purposes, such as backup, recovery from application corruption, testing, or migrating applications from server to server. The reasons for the copies are endless, and the SAN's flexible connectivity allows you to give the required storage to or take the storage from whatever server needs it.

Figure 10-1 shows the basics of Point-in-Time copy technology, ...

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