On Tue, 28 Mar 2000, Jesse Pollard wrote:
> --------- Received message begins Here ---------
> Marco Colombo <marco@esi.it>
> > On Mon, 27 Mar 2000, Linda Walsh wrote:
> >
> > > Khimenko Victor wrote:
> > > > There is small difference: there are disk quotas, but there are NO memory
> > > > quotas :-( Per-user ones, not per-process ones I mean...
> > > ---
> > > Maybe there need to be memory quotas. Dunno. But referring to the
> > > file system. It is the file doing the write that returns with an error
> > > code. Not another random process that happened to be using disk space. Also,
> > > reserving 5% (for root) isn't considered to be a horrible kludge to allow
> > > for recovery from such situations.
> >
> > But 5% reservation is not there for recovery from FS full situation.
> > Ext2 guys should drop a word here, but AFAIK it's mainly for performance
> > reasons (it was for FFS, where it was introduced the first time: at 95%
> > many allocation optimizations simpy failed).
>
> It was also made available to root to use so that syslog could continue
> to write to the root file system. Also, I believe pipe buffers were optionally
> stored in the root filesystem under tight memory conditions. Filling root
> with user data usually caused the system to hang trying to handle pipes and
> domain sockets (which syslog used...).
>
> The reserve then allowed the root user time to log in and clean up some
> things before the system died. Most user processes were put to sleep.
Just an useful side effect. 5% reserve was introduced for performance
reasons, i believe.
The root FS can be filled with *root* data, too. That's why syslogd writes
to /var/log. 5% reserve is not a great idea to avoid FS full. It helps
sometimes. No user processes should be allowed to write on the root FS,
anyway (yes, I hate /tmp, and /var/tmp, too).
> At least this was the case under UNIX System V release 2.
>
> -------------------------------------------------------------------------
> Jesse I Pollard, II
> Email: pollard@navo.hpc.mil
>
> Any opinions expressed are solely my own.
>
.TM.
--
____/ ____/ /
/ / / Marco Colombo
___/ ___ / / Technical Manager
/ / / ESI s.r.l.
_____/ _____/ _/ Colombo@ESI.it
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