Tom Reingold tommy@research.bell-labs.com writes
I believe it is not necessary to have quota trees in order to have quotas. But it is highly advisable. I highly recommend putting all user home directories in quota trees.
So do I, but not exactly for the reasons you give.
If you don't want to makefalse barriers, put all the users in a single quota tree. This will prevent a disaster. It's possible to have a disaster (well maybe the word is too strong) if your filer fills up. If it fills up, you could truncate an essential file such as /etc/passwd.
Not if safety-conscious procedures are followed when updating such files. But of course, a volume filling up can be a serious nuisance.
If the quotatree(s) add up to slightly less than the entire volume, then users will never fill up the filer.
True as stated, but in practice this will mean that your filer is under-utilised. The trick with quotas is _judicious_ overallocation. If you ensure that all your users working together cannot fill up the filer, you have overdone things: you just have to arrange that it would involve an improbably large conspiracy. :)
We put user home directories in a /home qtree, so that per-uid quotas can be made to apply only in that qtree (and the sum of the per-uid quotas is substantially larger than the size of the volume). There is a quota for /home as a whole, but with infinite limits; i.e. it's just for tracking usage. NFS access as root would escape all controls, but if this gets out the door we have a big hole in our security anyway!
Unfortunately, if existing directories are NOT in a quota tree, you have to move them into one. This can be extremely time consuming. I don't know a way around this. You may have to have a night where the filer is unavailable to users while you make the move(s).
To reorganise an already-populated volume like this is at least as painful as copying everything to a new volume. That's why it's worth advising NetApp-newbies to put everything (except /etc) into one or more qtrees from day one.
Chris Thompson Email: cet1 [at] cam.ac.uk