Help With Logical Volumes

Help With Logical Volumes

Post by Claude E. Watso » Thu, 28 Sep 2000 04:00:00



    I am another AIX newbie who is now administering a 7025-F50 running AIX
4.3.3 ML 04.  I need a pointer to the documentation for changing a vg.
    My problem at this time is that the person or people who set up this
machine set up two logical volumes that share two physical disks.  Both of
these logical volumes are the homes to very disk intensive processes and
those two disks show high usage.  Both processes also show intermittent
performance issues, which I attribute to disk I/O issues.  I have other
physical disks that are not assigned to vg's at this time, and I want to
move one of these to different disks.  Naturally this is a production box
that cannot come down during business hours, so taking anything offline is a
big issue.
    I've looked for this on the IBM site, and will be back there to look
some more as soon as I finish this message.  Any tips, hints, or pointers
are welcome.

Thanks in advance,
Claude Watson

Rookie AIX Admin

 
 
 

Help With Logical Volumes

Post by peter_rei.. » Thu, 28 Sep 2000 04:00:00




Quote:>     I am another AIX newbie who is now administering a 7025-F50
running AIX
> 4.3.3 ML 04.  I need a pointer to the documentation for changing a vg.
>     My problem at this time is that the person or people who set up
this
> machine set up two logical volumes that share two physical disks.
Both of
> these logical volumes are the homes to very disk intensive processes
and
> those two disks show high usage.  Both processes also show
intermittent
> performance issues, which I attribute to disk I/O issues.  I have
other
> physical disks that are not assigned to vg's at this time, and I want
to
> move one of these to different disks.  Naturally this is a production
box
> that cannot come down during business hours, so taking anything
offline is a
> big issue.
>     I've looked for this on the IBM site, and will be back there to
look
> some more as soon as I finish this message.  Any tips, hints, or
pointers
> are welcome.

> Thanks in advance,
> Claude Watson

> Rookie AIX Admin

Check out extendvg - but you might have to use chvg -t first ( if the
total number of PPs in the vg would exceed 1016 ).
Once you have included your spare disk(s) in the vg, you can migratepv
the lv(s) in question to the newly added hard disk(s), all while online.

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Before you buy.

 
 
 

Help With Logical Volumes

Post by Kurt Bremse » Thu, 28 Sep 2000 04:00:00




Quote:>     I am another AIX newbie who is now administering a 7025-F50
running AIX
> 4.3.3 ML 04.  I need a pointer to the documentation for changing a vg.
>     My problem at this time is that the person or people who set up
this
> machine set up two logical volumes that share two physical disks.
Both of
> these logical volumes are the homes to very disk intensive processes
and
> those two disks show high usage.  Both processes also show
intermittent
> performance issues, which I attribute to disk I/O issues.  I have
other
> physical disks that are not assigned to vg's at this time, and I want
to
> move one of these to different disks.  Naturally this is a production
box
> that cannot come down during business hours, so taking anything
offline is a
> big issue.
>     I've looked for this on the IBM site, and will be back there to
look
> some more as soon as I finish this message.  Any tips, hints, or
pointers
> are welcome.

> Thanks in advance,
> Claude Watson

> Rookie AIX Admin

Step 0: Have a backup ready!

I would recommend restructuring in a way so there are no shared disks
anymore; this does not imply setting up a new volume group.

Step 1: Add the disks to the vg (extendvg)

Step 2: Use migratepv with the -l option to move the LV's to the new
desired locations; watch out for pitfalls concerning the primary dump
device an VG's varied on in concurrent mode (see man migratepv)

Step 3: Watch if it has the desired effect :)
--
K.B.

"Es ist alles sehr kompliziert!" ("It is all very complicated!")
Fred Sinowatz, former Austrian Chancellor

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Help With Logical Volumes

Post by Claude E. Watso » Thu, 28 Sep 2000 04:00:00


    I hate following up to my own message, but I did find the Redbook and
should be OK now.

Thanks anyway,
Claude


>    I am another AIX newbie who is now administering a 7025-F50 running AIX
>4.3.3 ML 04.  I need a pointer to the documentation for changing a vg.

 
 
 

Help With Logical Volumes

Post by Claude E. Watso » Thu, 28 Sep 2000 04:00:00


    Thanks to Peter and Kurt I solved my problem, or at least one of them.
I still need to read the Redbook to learn more about it, but the system
likes having those disks split.
    Thank you both for your help.

Claude Watson




>>     I am another AIX newbie who is now administering a 7025-F50
>running AIX
>> 4.3.3 ML 04.  I need a pointer to the documentation for changing a vg.

 
 
 

Help With Logical Volumes

Post by Norman Levi » Fri, 06 Oct 2000 04:00:00





> >     I am another AIX newbie who is now administering a 7025-F50
> running AIX
> > 4.3.3 ML 04.  I need a pointer to the documentation for changing a vg.
> >     My problem at this time is that the person or people who set up
> this
> > machine set up two logical volumes that share two physical disks.
> Both of
> > these logical volumes are the homes to very disk intensive processes
> and
> > those two disks show high usage.  Both processes also show
> intermittent
> > performance issues, which I attribute to disk I/O issues.  I have
> other
> > physical disks that are not assigned to vg's at this time, and I want
> to
> > move one of these to different disks.  Naturally this is a production
> box
> > that cannot come down during business hours, so taking anything
> offline is a
> > big issue.
> >     I've looked for this on the IBM site, and will be back there to
> look
> > some more as soon as I finish this message.  Any tips, hints, or
> pointers
> > are welcome.

> > Thanks in advance,
> > Claude Watson

> > Rookie AIX Admin

> Check out extendvg - but you might have to use chvg -t first ( if the
> total number of PPs in the vg would exceed 1016 ).

** that is NOT total number of pps exceed 1016 - if pps in any SINGLE disk
would exceed 1016 ytou will need to use -t.

Quote:> Once you have included your spare disk(s) in the vg, you can migratepv
> the lv(s) in question to the newly added hard disk(s), all while online.

> Sent via Deja.com http://www.deja.com/
> Before you buy.

--
Norman Levin
 
 
 

Help With Logical Volumes

Post by nusra » Fri, 13 Oct 2000 04:00:00


We need to have some disks be writeable by one host,
but readable by many.  The locally-written application
that uses the disks ensures that each "owning" host
modifies only its own assigned-writeable disks.
(btw, when I say "disk" I mean physical spindle; each
spindle would be read-only to all hosts but one.)
Considerations:
-- for performance reasons, the disks should be "locally"
attached, i.e., not NFS.  A SAN-type solution would be ok.
-- for political reasons, we can't use HACMP, PPxx, HPFS,
etc.; it has to be "ordinary" AIX.
-- we can write whatever code might be needed, as long as
it doesn't require undocumented/unsupported interfaces.
-- we might be using EMC disks/frames, or IBM SSA disks.
-- for political reasons, we'd *prefer* to use JFS rather
than using raw volumes.
-- for budget reasons, we *might* not be able to use a SAN

Questions:
1.  Our biggest concern is OS/hardware glitches --
things like a host doing a bus-reset or permanent reserve.
What problems / solutions might we have in this respect?
What are the physical restrictions / requirements (e.g.,
cabling -- and what exactly is "twin-tailing")?
Can "hangs" be avoided without using a SAN?

2.  Would there be any special benefits of using a SAN
other than eliminating "hang" problems?  "Vanilla" AIX
has no special SAN-awareness that would eliminate the need
for us to do lock management in our application code, right?

3.  We're under the impression that mounting a volume as
read-only might eliminate some "hang" problems, but would
also cause that host to never refresh its cached directory
data after the mount.  We can think of ways around this --
e.g., by prepping each disk with fixed-size null-filled
files before the application ever uses it, so the inodes
never change.  But is this necessary?  Is there any way to
force AIX to physically access the directory on each open()?
(I don't think the O_DIRECT flag would help.)  btw,
repeated unmounting and re-mounting isn't an option.

Thanks in advance for your time, brain-strain,
and keystrokes, colleagues.
--bob
aka nusrat AT prodigy.net

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1. Using DiskSuite ufs logging on Volume Manager logical volumes?

Hi,

I am wondering if it is possible to use the ufs logging feature of
DiskSuite 4.1 on logical volumes defined by Sun Enterprise Volume
Manager 2.5, on a Solaris 2.6 system. I tried it with

# ./metainit d0 -t /dev/vx/dsk/rootdg/vol10 /dev/vx/dsk/rootdg/vol11
metainit: sun: /dev/vx/dsk/rootdg/vol10: Invalid argument

Just on the off chance that it is looking for slices with generic
c*t*d*s* names, I made symlinks to the logical volume files in the
/dev/dsk directory, and some other error came up

# ./metainit d0 -t c10t0d0s1 c10t0d0s0
metainit: sun: c10t0d0s1: already used in d0

So is there something fundamental that prevents setting up DiskSuite
trans metadevices (for ufs logging) using logical volumes? Or could it
be persuaded to work together? Are there alternatives for a logging
(journalling) filesystem aside from the following:

1. Get VxFS: too expensive.
2. Upgrade to Solaris 2.7+: need to support untested legacy
applications.
3. Get rid of Volume Manager and use DiskSuite to manage the disk array:
a lot of work here to backup data, define RAID metadevices and restore
data. Also slight loss of flexibility with the limit on slices.

Thank you very much for your suggestions.

Ed Young

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