[lug] Reserving part of a file system -- quotas or something else

[Vince Dean]

I have a system on which I would like to reserve a certain amount of
disk space for certain high-priority jobs, allowing all the users to
fight over the rest.  The machine runs a variety of research, ad-hoc
programs, alongside some high-priority production jobs.

Quotas sound attractive, but it's not obvious how to use them for this
purpose.  I could assign a quota to each user, but that would be far
more specific than I need.  I want either to reserve X Tbytes for one
use , or else limit the sum of all the other uses to Y Tbytes. I don't
need to manage quotas for each user.

One possibility would be to reserve an entire RAID, or an entire file
system for the production jobs.  This would work, but would limit our
future flexibility.

We have suggested using logical volume management to create the
partitions and to re-size them if necessary.  The system administrator
likes to use LVM for the initial setup of a system, but he is reluctant
to resize a logical volume, for fear of catastrophic data loss.  Is that
a reasonable fear?

Any suggestions?  Assigning entire machines or RAIDs to the production
jobs would certainly solve the problem, and might
be a better use of our time and money, but I would like to explore other
options.  Am I overlooking an easy solution?

Thanks,
Vince Dean