NetApp LUN creation/vol sizing

Well, as you might know I’ve been tinkering with a NetApp FAS at work. The last few months, I’ve been trying to figure out a few things, which I actually did.

One “error” I ran into with creating the lun’s and volumes by hand was that the volumes were running out of space. Even if the volume was a bit larger than the LUN. After that happened a few times, I decided to see how to fix that. As it turns out, the GUI “fixes” that already in a way I wouldn’t have expected.

The GUI wizard for creating a new LUN simply enlarges the hosting volume by three percent (that’s 3%!). So if you create a 300GiB LUN, the GUI will create a volume with 309GiB (well about that – the GUI calculates in KiB thus you’ll see something like 324009984k in the output of vol size).

I also wrote a short script, which will sum up the space of all LUNs contained inside a volume and then based on your snap reserve and the actual LUN space give you the current vol size and the vol size it should be. I’ll post the script later on.

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