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From: liam@cs.qmw.ac.uk (William Roberts;)
Newsgroups: comp.unix.aux
Subject: Re: Question on Partitioning Hard drive
Keywords: dp
Message-ID: <2865@redstar.cs.qmw.ac.uk>
Date: 21 Jan 91 13:38:19 GMT
References: <1991Jan17.231709.8562@zeno.mn.org>
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In <18805.27979475@windy.dsir.govt.nz> sramtrc@windy.dsir.govt.nz writes:

>My personal preference is to have separate root and usr partitions. The
>root partition is not written to very frequently and so you can fill it
>right up to, say, 99% full instead of 90%. That way you get an extra 9%
>disk space. 
Don't forget to leave room for autoconfiguration (i.e. about 1.5 megabytes if 
you have a separate tmp partition, twice that if you don't). Various things go 
very horribly wrong if your autoconfiguration fails and fills up what little 
space there is left in root: in particular root is the default SWAPDEV so 
spare blocks in root have to be available if you want pipes & 
command-redirection to work. The /etc/startup.d/ae6 file is not at all 
resilient to pipe failures!

>I used to recommend a seperate /tmp partition but that was
>in the old days of the svfs filesystem which used to keep inodes separate
>from files. The ufs filesystem does not have this problem since it spreads
>the inodes out over the disk. 

We have separate tmp partitions: partly habit but also so that we don't worry 
about the fact that root is full for normal users (who therefore can't make 
pipes: see above).

>Another possibility that I have not tried
>since it involves a lot of work is to mount the root partition read-only.
>That gives a margin of safety and means that you only have to do one 
>backup since nothing changes.

It won't work. This is a nice trick (Sun have done things to achieve this) but 
A/UX gets most of the advantages by doing an fsck BEFORE A/UX get launched 
(unless you turned that off as well as autorecovery).
--

William Roberts                 ARPA: liam@cs.qmw.ac.uk
Queen Mary & Westfield College  UUCP: liam@qmw-cs.UUCP
Mile End Road                   AppleLink: UK0087
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