🚀 go-pugleaf

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

In article <672@msa3b.UUCP>, kevin@msa3b.UUCP (Kevin P. Kleinfelter) writes:
> Why does AIX partition my lovely 300MB disk into "minidisks?"
> 
> Is there any reason why I should not just merge all minidisks except
> for root, paging, and dump into one "/usr"?    
> 
> You may reasonably ask, why do I care:
> Answer: If I have all my space in one partition, I'll never wish that
> I had given a greater percentage of my space to that partition!
> 

It is rather obvious that this person was(is) IBM/VM/CMS damaged.  :-)

The reason for partitioning is several fold. 

1)  Large file systems make large lists that need to be traversed to find/
	 consolidate free space.  Small file systems will be faster.  (Speed)

2)  Physical head motion can be reduced as a file cannot be spread across
	 the entire disk.  (Locality)

3)  Dangerous file systems cannot corrupt important ones.  (/usr/spool/news
	 might grow without bound when deluged by another machine testing CNews.
	 This overflow won't affect my precious data in my home directory because
	 the file systems are completely decoupled.)  (Decoupling)

4)  A large contiguous file system, when damaged or obselete is harder to 
	 replace or workaround than several smaller file systems.  (A 300 Meg file
	 system is a bear to put onto several 160Mb drives when you get moved
	 to a new system.  Several 80Mb file systems can go anywhere with you.
	 Plus your precious data isn't all over system dependent garbage.  It
	 is partitioned physically and logically.)  (Maintainability)

5)  Removable media make several filesystems that are interchangeable very
	 easy.  Of course, if everything is on one big partition, each pack must
	 duplicate the entire environment.  Put seldom changed files (/bin) onto
	 permanent storage.  Put fast changing but temporary (/tmp) onto the more 
	 permanent storage.  Use removable file systems for only those files that 
	 need to be removed.  It is seldom a good idea to put /tmp and /bin on
	 removable media.  So, partition sensibly and save yourself the hassle.
	 (Interchangability)

Any more?





-- 
David F. Carlson, Micropen, Inc.
micropen!dave@ee.rochester.edu

"The faster I go, the behinder I get." --Lewis Carroll