Thoughts on Quotas

Samuel J. Greear sjg at
Tue Sep 28 01:45:08 PDT 2010

On Mon, Sep 27, 2010 at 10:34 PM, Chris Turner
<c.turner at> wrote:
> Samuel J. Greear wrote:
>> 2^16 is nowhere close to enough. Quota's are very useful and to be
>> useful you need to support hundreds of thousands of users. I consider
>> lack of useful quota's to be one of our most major deficiencies.
> show me a single unix system with 100k's of users?
> I'm sure there's a few. but not 'hardly useful' if not supporting
> less than 100k
> also:
> $ grep 'uid_t;' /usr/include/sys/types.h
> typedef __uint32_t      uid_t;          /* user id */
> so like.. 32768 < 100k
> which isn't to say unix user/groups etc. is be-all-end-all
> of "user systems" -
> but it works pretty well for most cases - and this statement
> quite simply *not true* - run a workgroup lan for like 5 minutes -
> and you'll find that 'hey this quota thing is a good idea'

Virtual hosted mail, real disk quota's tend to be much more efficient
and easy to manage than ad-hoc quota systems enforced by both an SMTP
server and POP/IMAP server. In this case every virtual mail account
gets a real uid within some range, but not an /etc/passwd entry or
etc. -- This is definitely not an uncommon configuration.

Mass virtual hosted shared website hosts are in some cases cramming in
the low 10,000's web accounts onto a single server now on relatively
commodity hardware. That number will be in the hundred thousands 5
years from now, I suspect.

HAMMER is an amazing filesystem to use as the underpinnings of a
backup platform or NFS host for multiple head servers or etc., when
you have a dozen or more machines hanging their storage off of one
(maybe dozens or hundreds of heads in the future, when we see
clustered HAMMER) pressure on uid's/gid's goes through the roof.

Quota systems are also often overloaded for accounting purposes, so
before you think "well, quota's aren't useful in that scenario!", I
have definitely tied quota's into billing at more than one employer
under different scenarios in which the quota systems didn't actually
enforce any limits on storage utilization. As an aside, perhaps this
should be considered for any future quota implementation.

It is certainly possible that I am in the minority, but I definitely
see hundreds of thousands as necessary now, it will be millions in the

That isn't to say I think being able to place limits on a pfs is
necessarily a bad idea, I can think of uses. Reservations might be
useful too. I just don't see it replacing a quota system.


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