Dell Compellent – Preallocating storage

In my first post on the Dell Compellent, I’d mentioned that it was possible to preallocate storage on the array, even though it was thin by default. I can’t really think of a reason why you’d want to do this on this particular array, but here’s how to do it.

Firstly, create the volume but don’t map it to anything. Then wait a little while. I can’t remember how long, but it’s a little while. Then right-click on the volume and the option to “Preallocate Storage” will be there.

CML_Pre1

You will be warned that you’ve basically turned your back on years of hard work by the Compellent developers. Think about that.

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When it says it will take several minutes, it’s not lying.

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It will probably take a lot longer than several minutes, particularly if you’re making a 20TB volume, like I am.

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In fact, the array will get a bit concerned about how long it’s taking as well.

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Five hours later, and about 7.5TB has been preallocated.

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Here’s a picture of it when it’s finished. Note the lack of space.

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You’ll also notice that the storage is in conservation mode now, basically because there’s not a lot of space left to work with.

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You can right-click on these alerts to “Clear Emergency”. Note, however, that you need to have actually cleared the emergency (made space, for example), before you can, er, clear the emergency.

CML_Pre9

Note also that it takes a little while to delete a 20TB volume.

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And there you have it. It is possible, and there might even be a reason for doing it. But then you might just have bought the wrong array for the job.