If the volume is full then this will then take the LUN off line to ensure that your Windows environment doesn’t try to write to a LUN that no longer has space in its supporting volume.
The LUN itself can also fill up dependent on the type of things going on…If there is a lot of adding and deleting files then this can take up LUN space, even though Windows thinks there is plenty of space…
Space reclamation frees that space up…but does create a big backup next time around.
But start with checking available volume space and go from there…
The reason the LUN goes off line is what can happen is that Windows can think the LUN still has space available to it, however the LUN at the backend can actually be full because of things like data been deleted etc…so although Windows thinks that data has gone…the filer at the back end just sees the deletion as block changes in the LUN.
You need to do a space reclamation on the LUN to get that space back…always useful if the data on the LUN changes on a regular basis.
So there is no option that I’m aware of to stop a LUN going off line…it does that to protect itself from and OS trying to commit data when no space exists in the LUN or the NetApp volume that it is in.
Things like SQL can cause this, especially if the lun has transaction logs on it…as they can change a lot.
If you have SnapDrive installed on your server, hopefully you have, its an option in snapdrive, you’ll see it down the left hand panel.
If you’re not using SnapDrive on your windows server, I’d suggest well worth getting a copy from the NOW site and installing it on the Windows server, it will give you much better integration between the NetApp and Windows environment.