[TUHS] Quotas - did anyone ever use them?

Nelson H. F. Beebe beebe at math.utah.edu
Fri May 31 10:21:02 AEST 2019

Several list members report having used, or suffered under, filesystem

At the University Utah, in the College of Science, and later, the
Department of Mathematics, we have always had an opposing view:

	Disk quotas are magic meaningless numbers imposed by some bozo
	ignorant system administrator in order to prevent users from
	getting their work done.

Thus, in my 41 years of systems management at Utah, we have not had a
SINGLE SYSTEM with user disk quotas enabled.

We have run PDP-11s with RT-11, RSX, and RSTS, PDP-10s with TOPS-20,
VAXes with VMS and BSD Unix, an Ardent Titan, a Stardent, a Cray
EL/94, and hundreds of Unix workstations from Apple, DEC, Dell, HP,
IBM, NeXT, SGI, and Sun with numerous CPU families (Alpha, Arm, MC68K,
SPARC, MIPS, NS 88000, PowerPC, x86, x86_64, and maybe others that I
forget at the moment).

For the last 15+ years, our central fileservers have run ZFS on
Solaris 10 (SPARC, then on Intel x86_64), and for the last 17 months,
on GNU/Linux CentOS 7.

Each ZFS dataset gets its space from a large shared pool of disks, and
each dataset has a quota: thus, space CAN fill up in a given dataset,
so that some users might experience a disk-full situation.  In
practice, that rarely happens, because a cron job runs every 20
minutes, looking for datasets that are nearly full, and giving them a
few extra GB if needed.  Affected users in a average of 10 minutes or
so will no longer see disk-full problems.  If we see serious imbalance
in the sizes of previously similar-sized datasets, we manually move
directory trees between datasets to achieve a reasonable balance, and
reset the dataset quotas.

We make nightly ZFS snapshots (hourly for user home directories), and
send the nightlies to an off-campus server in a large datacenter, and
we write nightly filesystem backs to a tape robot. The tape technology
generations have evolved through 9-track, QIC, 4mm DAT, 8mm DAT, DLT,
LTO-4, LTO-6, and perhaps soon, LTO-8.

Our main fileserver talks through a live SAN FibreChannel mirror to
independent storage arrays in two different buildings.

Thus, we always have two live copies of all data, and third far-away
live copy that is no more than 24 hours old.

Yes, we do see runaway output files from time to time, and an
occasional student (among currently more than 17,000 accounts) who
uses an unreasonable amount of space.  In such cases, we deal with the
job, or user, involved, and get space freed up; other users remain
largely remain unaware of the temporary space crisis.

The result of our no-quotas policy is that few of our users have ever
seen a disk-full condition; they just get on with their work, as they,
and we, expect them to do.

- Nelson H. F. Beebe                    Tel: +1 801 581 5254                  -
- University of Utah                    FAX: +1 801 581 4148                  -
- Department of Mathematics, 110 LCB    Internet e-mail: beebe at math.utah.edu  -
- 155 S 1400 E RM 233                       beebe at acm.org  beebe at computer.org -
- Salt Lake City, UT 84112-0090, USA    URL: http://www.math.utah.edu/~beebe/ -

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