From: fritz@scipp.UCSC.EDU (Frederick Staats)
Newsgroups: comp.unix.aix
Subject: Re: How Do You Partition A Disk In AIX?
Date: 9 Apr 92 18:10:34 GMT
Organization: Santa Cruz Institute for Particle Physics

Sam Drakes comments are good... here are a few of my own...

In article <1633@rufus.UUCP> drake@drake.almaden.ibm.com (Sam Drake) writes:
>In article <1412@newave.UUCP> john@newave.mn.org (John A. Weeks III) writes:
>>Can someone give me some pointers or point me to a place in a
>>manual?  Smit seemed to be no help--it has a bunch of stuff on
>>logical volume groups, which seem to assume that you have the
>>partitions already made.

Look up the book General Concepts and Procedures in the IBM
documentation (it is available in hard copy as well as InfoExplorer.)
It has good overviews on "Logical Volumes", "Paging Spaces", and "File
Systems". It is _DIFFERENT_ than on other UNIX systems and you _NEED_
to read the documentation.  It is a pain to learn a new system but it
is one of the few places that IBM has done a much better job than any
other UNIX vendor.  The system is more robust, easier to use (once you
understand it), and more flexable than the BSDish (SunOS), and SYSVish
filesyetems.

>No, the logical volume manager is where you want to go.  
>
>First, you have to decide if you want to put both volumes into
>a single volume group (rootvg), or if you want the 2nd volume
>in a separate group.  If it's in a separate group, you can't have
>a filesystem that spans volumes.  If you want a separate group,
>think up a name for it.  Unless you need a >400MB filesystem, I'd make
>both disks separate volume groups.

Note: Volume Groups and Logical Volumes are limited to 2 GBytes not a
problem for a small stand alone machine, but on our server where we
use 1.7 Gbyte drives only one physical volume (we don't do mirroring)
will fit in a Volume Group.  I can understand that it can be hard to
make a filesystem fast if it is larger than ~2-4 GBytes, but it would
nice to have a larger volume groups.  Now that people are selling RAID
arrays with 10 GBytes of addressable storage and CDROM judeboxes that
store even more it makes sense to think BIG.  It would also be nice to
have a "LargeJFS" that had an unlimited size even if it was slightly
slower.  (We have users that want to copy 5-25 GBytes data off 8mm
tape, process it for a few days and copy the results back onto tape.
It would be real nice if I could give them a file system large enough
to do that.  Of course the individual data files from the tape are
only in the 32Kbyte-200MByte range and fit into real memory, they just
have alot of them to process.  We live with staging parts of the data
off tape, processing it and then grabbing more.  I've got one group
that wants to process 1000 8mm 2.3 Gbyte data tapes in the next year
alone.  We have a couple 10 tape Exabyte EXB-10i stackers with with
Exabyte 8500s in them, and are looking for someone who sells a SCSI
driver for the RS/6000.  Anyone out there sell just a driver for the
Exabyte EXB-10i's, we already own the stackers and don't want to buy
any more... just need the driver?)

>To see how much space is available in a volume group, or what resides
>on which physical volume, go spelunking in "logical volume manager"
>under "physical and logical storage".  

This is a nice feature, a utiltiy with a better user interface would
be helpful.  It can become hairy trying to manage a complicated
multi-disk Volume Group where you purposely place the filesystems logs
on seperate Physical Volumes from the data (for the speed advantage.)
It has been hard enough to do the planning and analysis that I've only
played with these features once or twice.

>>I assume that I have to do some mkdev's, then mkfs, then mount,
>>but I cannot find docs on the proper device names for mkdev,
>>or the number of sectors for mkfs.
>
>As described above, those assumptions are incorrect.  I hope you'll agree
>that the function and flexibility provided by the AIX mechanisms are
>worth learning something a bit new.

Yes they are powerful and I think worth learning.  But the command
line interfaces are not much better than what you have on other UNIX
systems so there is resistance from some users to yet another system
that isn't any easier to use.  Once you understand how it works it
will make your job easier, but _READ_ the documentation.

>Sam Drake / IBM Almaden Research Center 
>Internet:  drake@almaden.ibm.com    BITNET:  DRAKE at ALMADEN


-- 
Frederick Staats
fritz@scipp.UCSC.EDU -- (408) 459-3575
Santa Cruz Institute for Particle Physics
University of California at Santa Cruz