Very Computer

Hey.

I'm in a situation in which I'm having to bone up on a bunch of VxVM
stuff w/o access to a system: doing it all by reading Veritas manuals
and SunOS/VxVM man-pages on the web, and taking notes (which helps me
learn).  A few weeks ago, I looked for Veritas-dedicated Usenet groups
and found none (on Google groups); so, I'm sending to y'all in the hope
that a bunch of VxVM experts contribute here.  If you think there's a
better place for me to ask my VxVM questions, please let me know.

One big catch, to my studying the way I am, is the typical
inconsistencies in the ways the documentation-writers have expressed
the various concepts and meanings of things, plus the holes (the things
they mostly or completely leave out).  Right now, here's the thing
that's bothering me most:

Looking at the VxVM-3.5 Admin Guide (PDF) and at the vxmend(1M) and
vxplex(1M) man-pages from docs.sun.com, it is *VERY* unclear as to the
distinction between "detaching a plex", as with the command "vxplex det
<plex_name>", and "offlining a plex", as with the command "vxmend off
<plex_name>".  It is clear that the latter changes the plex's "STATE"
(vxprint output) to "OFFLINE" but it is *not* clear that the former
does not also do so, or, if not, what "STATE" the former does change
the STATE to.

I *do* understand about following up "vxmend off" (STATE set to
OFFLINE) with "vxplex att" (STATE set to STALE) and then "vxvol start"
(by hand or during reboot) to get the plex back up & running with the
rest of its volume's components.  But would/could I ever use "vxmend
off" and "vxplex det" for precisely the same situation and intentions,
or must I use "vxmend off" for one set of situations and "vxplex att"
for a completely different set of situations; or are some situations
different and others overlap?

TIA for anybody's help with this!!!

#####################
John Reed Avery

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aude sapere
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The way I understand it is the difference is that detaching a plex
actually removes it from the volume.  It still exists as a plex but it
is no longer a part of any existing volume.  Offlining a plex in a
mirror stops any new writes to that plex but leaves it as a part of the
volume. I have used detaching a plex mostly for later attaching it to
another "temporary volume" for backing up the filesystem.  I also have
used detaching a plex to "fix" a mirror that has had a disk failure on
one side before replacing the failed drive when I had extra space on
other drives.  I can't think of any time that I have used the vxmend
offline command except maybe in a trouble fixing/troubleshooting
situation.  Perhaps others will chime in.

Wayno and everybody, I think I figured it out.  It was right there in
front of me the entire time but it was expressed as a casual comment,
amongst a bunch of other info.  According to each the VxVM-3.5 Admin
Guide and the VxVM-4.0 Admin Guide:

*    When you do a "vxmend off" command, the plex's STATE
     (vxprint output) is set to OFFLINE and the plex is *not*
automatically recovered upon the next reboot or the next manual running
of the "vxvol start" command.

*    When you do a "vxplex det" command, the plex's STATE
     (vxprint output) is set to STALE and the plex *is* automatically
recovered upon the next reboot or the next manual running of the "vxvol
start" command.

Thanks and sorry for wasting the bandwidth.  :-/  

--JRA

I don't know of any other newsgroups, but there is a VxVM admin mailing
list.  Go to http://mailman.eng.auburn.edu/mailman/listinfo/veritas-vx/

--

Senior Technical Consultant         TAOS            http://www.taos.com/
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