Multiple partitions on 1 and 2 Unix PC hard disks.

[Karl Swartz]

In article <1323 at icus.ICUS.COM> lenny at icus.ICUS.COM (Lenny Tropiano) writes:
>In article <1990Nov16.033801.978 at shibaya.lonestar.org> afc at shibaya.lonestar.org
>|>My original plan is to make 2 partitions of equal size in this new disk:
>|>/ and /u.  The pros and cons, as I see them are:

You can probably do better with some careful thought and tuning, but
there are risks.

>Be careful with partitioning.  While there is some benefit to multiple
>partitions on the UNIX PC (if your disk space warrants it) [ie. the
>fragmentation problems with some highly-volitile areas] -- the UNIX PC
>software wasn't designed with that in mind.

In particular, many systems have a minimal / or root partition, just
enough to boot the system, then a larger /usr partition that is needed
for normal system operation but not for a minimal boot.  This makes a
lot of sense, but there's stuff in /usr that the UNIX PC wants to have
long before you'd get around to mounting any partitions, so don't try
this trick.

The other major gotcha is with installations that try to link to /usr
from /tmp, assuming you mount /tmp.  Fortunately this is a simple task
of unmounting /tmp for the duration of any software installs.

>Nevertheless, partitions do work.
>
>/ on /dev/fp002 read/write on Sat Nov 10 15:32:10 1990
>/tmp on /dev/fp003 read/write on Sat Nov 10 15:32:10 1990
>/usr/spool on /dev/fp004 read/write on Sat Nov 10 15:32:10 1990
>/usr/tmp on /dev/fp011 read/write on Sat Nov 10 15:32:10 1990
>/netnews on /dev/fp012 read/write on Sat Nov 10 15:32:10 1990
>/archives on /dev/fp013 read only on Mon Nov 19 22:15:28 1990

Yup, and mine looks quite similar:

/ on /dev/fp002 read/write on Sun Nov 18 13:26:55 1990
/tmp on /dev/fp011 read/write on Sun Nov 18 13:27:07 1990
/usr/spool on /dev/fp004 read/write on Sun Nov 18 13:27:43 1990
/u on /dev/fp003 read/write on Sun Nov 18 13:29:25 1990
/u2 on /dev/fp005 read/write on Sun Nov 18 13:30:18 1990
/usenet on /dev/fp012 read/write on Sun Nov 18 13:31:04 1990

My /archives is called /u2, and I keep /u separate but not /usr/tmp.
These latter two deserve comment.  First, I occasionally login as
install, and somewhere along the way this got bent out of shape when
it found it wasn't in the root partition.  I solved this by moving
install's home directory to /ua.install.

/usr/tmp isn't so easy.  I initially 5 MB each for /tmp and /usr/tmp.
After seeing some weird behavior with news history files, I realized
that the 5 MB in /usr/tmp was not enough scratch space for sort when
doing a Usenet expire.  But I didn't want to reduce the size of /tmp.
The only significant use of /usr/tmp was sort, so it seemed to try to
move sort's scratch area to /tmp and switch to a 10 MB /tmp without
any special space for /usr/tmp.  (I ended up using only 7.6 MB for the
merged /tmp partition.)  To do this I found I had to patch the sort
executable, which I did as follows:

    # cd /bin
    # cp sort sort.usrtmp
    # adb -w sort
    > 0x90440?s
        90440:   /usr/tmp
    > 0x90440?W '/tmp'
    > 0x90444?w 0x74
    > ^D
    #

>|>Also, would it do any good to have a swap partition larger than 5000 
>> blocks?  (I also plan to add 1.5 Mb RAM to a RAM-less combo board.)

I've found it very easy to outstrip that rather paltry allocation, so
increasing swap space is now one of the first things I do on a UNIX PC.

Anyway, ditka has a Maxtor XT-2190 as drive 0 and the original MiniScribe
6085 as drive 1, with partitioning as follows:

    drive  partition  blocks  inodes  filesystem
      0        0         120     -    (VHB)
               1       9,000     -    (swap)
               2      42,000  10,496  /
               3      36,000   8,992  /u
               4      16,200   4,048  /usr/spool
               5      43,560  10,880  /u2
      1        0          64     -    (VHB)
               1       7,680   1,920  /tmp
               2      57,792  24,000  /usenet

VHB is the Volume Home Block, which contains the drive partition table,
bad block table, and perhaps a loader.  The intent of the distribution
of files was to spread the load of news activity over both drives (note
that /usr/lib/news ends up on drive 0) and to restrict the second drive
to fully expendable information.  Also, I wanted to minimize seeking on
drive 0, so /u2 (archival storage) is out of the way, and /usr/spool is
a bigger seek than /u from the executables which is probably better for
my purposes.

I also gave /usenet (the partition used to hold news articles) roughly
twice as many inodes as the default, using the following command:

    /etc/mkfs /dev/rfp012 115584:24000 1 128

In retrospect, I'd give serious consideration to putting /usr/lib/news,
or at least the history files, in a separate partition, as this tends
to fragment its home fairly quickly.  Otherwise, this arangement has
served my needs well.

-- 
Karl Swartz		|UUCP	{uunet,decwrl}!daver!ditka!kls
1-408/223-1308		|INet	kls at ditka.chicago.com
			|Snail	1738 Deer Creek Ct., San Jose CA 95148
"It's psychosomatic.  You need a lobotomy.  I'll get a saw."