SUMMARY : Digital Unix Filesystems (cf. AIX and JFS)

From: chas <sweeting_at_neuronet.com.my>
Date: Sat, 29 Mar 97 20:34:58 -0000

I initially asked 3 questions in one email to the list.
Due to the large amount of information / responses, I have split
the summaries up into 3 separate entities.

Huge thanks and respect go out to all of the OSF-managers who
generously took the time to help. Thanks go to Erik Persson,
Larry Church, Subir Grewal, Barb Baker, Mikel Stous, Karl Marble,
alan_at_nabeth.cxo.dec.com, paw_at_northstar.dartmouth.edu and
 Anil Khullar . I do hope I have not missed anyone out.

As others have mentioned, it is truly amazing how fast
replies / answers come in - OSF-managers is an awesome
list and this system of summaries (to keep traffic low)
is ideal.

Thanks again. (the original question and summary follow)

Chas


> 3) How do you find the physical volume of the HD ?
> Whereas AIX by default gave minimal filesystem
> volumes and then left it to the sysadmin to
> add more space or filesystems as required, I think
> that my entire HD has been split between :
> /
> /proc
> /usr
> Is that the OSF way ? to split the entire physical volume
> on installation of the OS ?

summary : not sure how to write this so i have included advice
from the OSF-managers. probably the biggest lesson for me though
is summed up by paw_at_northstar.dartmouth.edu

"You may want to get a copy of the DU sysadmin guide."

sure wish we had it..... i previously checked the archives and
found a previous posting that said that there are no DU specific
 books and that the Evi Nemeth et al Sysadmin Book is the best
resource. I have asked around here and apparently, the Alphas
didn't come with any documentation whatsoever. :(

anyway, here is what others said ......


====== [ Anil Khullar ] ======
That is correct. If you initially had more disks, and chose
to use AdVfs instead of ufs, it would prompt you for it.
With advfs you can add slices to the domain.


==== [Erik Persson] ======
Yup, that's basically the way it works - if you're using regular UFS
filesystem. Partition sizes will be static in size. A better way is to
use the Digital Advance Filesystem (advfs) instead. Then you get
filesystem logging, the possibility to add more disks or/and
filesystems on the fly and so forth. The / filesystem still needs to
reside on a seperate partition but that's only somewhat less than 100
MB. The proc filesystem is not a real filesystem but rather a pseudo
filesystem where process and memory info can be read in an easier way
than reading /dev/kmem directly.


==== [Larry Church] ======
AIX uses a Logical Volume Manager to do the disk space allocation -- an
additional level of abstraction between the physical disk drive. The DU
default
file system is at a lower level. The UFS filesystem is older and
simpler. The
ADVFS filesystem similar to the AIX LVM filesystem.

The /proc file system is special and doesn't really exist.

The disklabel utility will allow you to see the disk partition
information.
Below you see that /dev/rz3 contains 8386733 512 byte blocks or 4.2
GigaBytes.
Also note that disklabel wants the character device name of the disk
(/dev/rrz3a).



==== [Subir Grewal] ========
Most people prefer to partition their disks between / and /usr. You could
use just one big partition, but that might create various problems in case
of a disk error, some files getting overly large, hence bringing the
system to a standstill, etc. Look up commands like df, format, mount,
etc.


===== [Mikel Stous] ========
I would minimumly have a /, /usr, and /home (/var in /usr or /)

Personally, I would also have /usr/local as a separate
filesystem and /var in /. That way I only have to
backup / and /home constantly, /usr/local on a frequent basis,
and /usr only once in a while.

/proc is a virtual filespace. It only exists in the computers
ram to help manage processes.


===== [Karl Marble] =========
/proc doesn't take up any space. It's a tool for programmers to access
processes as if they were files. If you don't want it (and be sure your
applications don't need it) comment out its entry in /etc/fstab.

Not sure what you mean otherwise. The way you split things up is totally
up to the administrator, and at the fundamental level you only do things
when you install the system software. Tools like Logical Storage Manager,
and Advanced File System give you some more flexibility but are quite
complicated.

===== [alan_at_nabeth.cxo.dec.com] =====

        3. Digital UNIX uses a partitioned system disk. The
            root file system is at the beginning of the disks
            and typically between 32 and 128 MB. This is followed
            by the primary page/swap space which doesn't contain
            a file system and is used as a raw device (it doesn't
            show up on df(1), so use swapon(8) to see what spaces
            are used). In the factory installed systems, this is
            followed by /usr which is typically the rest of the
            disk.

            /proc is a file system representation of the process
            table and doesn't use any space on disk.

            The installation procedures give you the option of
            spliting /var from /usr and most who chose the option
            will use a partition on the system disk. When you
            use UFS as the file system, the device name and partition
            are clearly shown in the df(1) listing. If you use
            AdvFS for the file system, you have to show the domain
            to see what devices are in it.



===== [paw_at_northstar.dartmouth.edu]
It depends. You may be running AdvFS, which is more like IBM's JFS - if
you are, you'll see mention of it in the startup messages, and your df
will
report things other than normal /dev/rz?? for the partitions. Note that
/proc is *not* a physical partition on a disk - it's a virtual file system
(the process space) - read the man page.




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Received on Sat Mar 29 1997 - 13:48:47 NZST

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