Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ukma!gatech!bloom-beacon!spdcc!dyer
From: dyer@spdcc.COM (Steve Dyer)
Newsgroups: comp.sys.ibm.pc.rt,comp.unix.i386
Subject: Re: Why minidisks?
Message-ID: <3794@ursa-major.SPDCC.COM>
Date: 20 Jul 89 15:58:49 GMT
References: <672@msa3b.UUCP>
Reply-To: dyer@ursa-major.spdcc.COM (Steve Dyer)
Organization: S.P. Dyer Computer Consulting, Cambridge MA
Lines: 38

In article <672@msa3b.UUCP> kevin@msa3b.UUCP (Kevin P. Kleinfelter) writes:
>Why does AIX partition my lovely 300MB disk into "minidisks?"
>I understand the need for a paging minidisk (partition) and a dump
>minidisk (partition).  Also, I can make a good argument for a
>separate root minidisk.  The thing I don't understand is why have
>	/
>	/u
>	/machinename
>	/machinename/tmp
>	/whatever-else-you-create-to-fill-rest-of-300MB
>Is there any reason why I should not just merge all minidisks except
>for root, paging, and dump into one "/usr"?    
>(P.S. If it matters, this is AIX PS/2 1.1.)

AIX RT doesn't require minidisks of the form /machinename.
AIX PS/2 does, and both / and /machinename are implicitly mounted at 
boot time.

This is undoubtedly an attribute of the yet-to-be-released TCF
facility in AIX PS/2 and AIX 370, wherein a collection of PS/2s
and/or 370's all share the same extended filesystem, including a
common root.  Files formerly found in /etc which are "private"
to a particular machine have been moved to /machinename.  On most
UNIX systems these days, /tmp is a smallish partition of its own,
and under TCF, placing it under /machinename/tmp makes sense, since
having a global shared /tmp is risky, given that most UNIX systems
presume that /tmp is private (e.g., composite filenames consisting
of a string+PID will no longer be unique.)  /tmp is a symlink to
/machinename/tmp.  Similarly, the per-machine files which used to
reside on /etc (and elsewhere) are now symlinks to files on /machinename.

TCF hasn't been released yet, but much of the code (and all of the
design) to support it is already present in AIX PS/2 1.1.

-- 
Steve Dyer
dyer@ursa-major.spdcc.com aka {ima,harvard,rayssd,linus,m2c}!spdcc!dyer
dyer@arktouros.mit.edu