OT: redhat

[Bill Campbell]

On Sat, Nov 13, 2004, Bill Vermillion wrote:
>Shakespeare wrote plays and sonnets that will last an eternity, 
>but on Sat, Nov 13 14:32 , Bill Campbell wrote:" 
>
>> On Sat, Nov 13, 2004, Jay R. Ashworth wrote:
>>
>> >On Tue, Nov 09, 2004 at 11:42:50AM -0800, Bill Campbell wrote:
>> >
>> >> On Tue, Nov 09, 2004, Fairlight wrote:
>> >>
>> >> >Confusious (Jay Ashworth) say:
>
>> >> >> On Mon, Nov 08, 2004 at 09:43:13AM -0500, Bill Vermillion
>> >> >> wrote:
>
>> >> >> > Sure you can add pieces and expand a filesystem anytime
>> >> >> > you want >if< you have the right OS. :-) :-) :-) AIX is
>> >> >> > the only one that I know of that does that. :-(
>
>> >> >> SuSE 9, XFS.
>
>> >> >Filesystem is not the question. PHYSICAL PARTITION (as
>> >> >in...think fdisk, folks) is the issue. I'm talking about
>> >> >needing to join two disparately located partitions into one
>> >> >partition and expanding the fs that's on one of them to
>> >> >include the space on another.
>
>> >> The Linux LVM (Logical Volume Manager) or FreeBSD vinum
>> >> provides this capability. There's an interesting feature in
>> >> thsi month's Linux Journal on the unionfs which provides
>> >> some very interesting capabilities joining multiple file
>> >> systems types including file system snapshots, software
>> >> versioning, and others which I'm not sure I understand yet.
>
>> >Forgive me; of course this is a two parter.
>
>> >LVM lets you add more physical partitions on to a logical one;
>> >XFS lets you enlarge an active filesystem to take advantage of
>> >the new space.
>
>> On Linux systems, you have programs that will resize existing
>> partitions, /sbin/resize2fs, and /sbin/resize_reiserfs on a
>> SuSE 9.0 Professional box here which handle ext2/3 and reiser
>> file systems. FreeBSD has a program, growfs, to handle the job.
>
>I'm not familiar with the SuSE offerings but growfs will only
>let you grow a file system.
>
>The big confusion in the BSD world vs the rest of the world
>is the definition of partitions.  In BSD those are slices.
>And if you want to use growfs beyond the boundary of a slice
>[called a partition in the rest of the world] you have to
>resize the slice with fdisk, and then once slice is larger
>you can enlarge the system with growfs.

In that respect FreeBSD is similar to SCO Xenix and OpenServer which uses
divvy to break a ``partition'' into logical file systems.

>If you look back at the attributuions I mentioned AIX was the only
>one I knew of that could expand dynamically. growfs requires an
>unmounted fs, and while not an AIX expert [or as that AIXpert?]
>I understood that it's facility would expand on a running system.

I think that AIX is based on the Veritas file system which has many neat
features including ``freezing'' a partion for backup while journalling
changes which can then be used to update the frozen system.  Veritas has
been ported to systems other than AIX.

>Then Jay mentioned SuSE 9 XFS.

XFS was originally written by SGI and released to the Linux world as open
source.

>Then Mark [aka Fairlite] mentioned joining two physically disparate
>partitions to be able to make a larger FS.   I can see that will
>be problematic at least in the Intel based world as everything 
>expects 4 physical partitions, one of which will be active.

There can only be four ``primary'' partitions using PC standard
partitioning or three primary and an ``extended'' partition which can
contain multiple logical partitions.

The more advanced systems such as vinum and LVM can span partitions and/or
hard drives so there's no physical limitation.

>Each partition must occupy contiguous disk space.  So to
>use space on more than one partition [BSD slice] that are not
>physically adjacent the fileysystem creation programs would handle
>that at the logical level.  I don't see the need for having to
>physically join partitions to make a file system if you can
>logically create a filesystem spread over more than one
>physical partition.

The only time I've used LVN on Linux to join disk partitions was to join
two 2gb partitions into a 4gb logical partition where I didn't want to
change the partitions with fdisk for fear of breaking things that knew
about the partition numbers.

Bill
--
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