[linux-lvm] LVM Questions

Thu May 3 11:15:44 UTC 2001

On Wed, May 02, 2001 at 06:45:59PM -0700, Evan Day wrote:
> Darren Young wrote:
> > First, does LVM do RAID or do I need to employ the md
> > driver to accomplish this? It seems to me (as a
> > sysadmin) that LVM is great for adding space when
> > needed, but having RAID capabilities in conjunction
> > with this would be required to produce a highly
> > available system.
> 
> LVM doesn't do RAID right now - you can use either a hardware
> RAID or the kernel's built-in RAID support (raid 0, 1, and 5).

Evan is right for RAID > 0.

RAID 0 is supported in Linux LVM natively.

You could for eg. address your availability needs with MD or hardware RAID
*and* your performance needs at the same time by setting up RAID 0 logical
volumes striped over a bunch of RAID subsystem based physical volumes.

> 
> > What ext2 resize utility is the ideal choice for LVM
> > to use. parted seems to be quite functional, but
> > having to down the machine to single is a but
> > annoying. Has anyone successfully used the ext2online
> > utility on RedHat? It seems as though the version of
> > e2fsprogs that includes this code is part of RH 7.1
> > anyways. At least from what I can tell. The online
> > resizing would definitely be required for a highly
> > available system as well.
> 
> I don't have much experience with ext2 resizing, but the
> reiserfs can easily be extended.  I'm not sure if it is
> supported or not, but I've actually extended filesystems
> while mounted with no ill effects.
> 
> Reiserfs support is built in to kernel 2.4.X.

WRT ext2 you could give Andreas Dilger's ext2resize GNU software a try.

Please look for it at http://ext2resize.sourceforge.net/.

> 
> > I started with RedHat 7.1 with the 2.4.2 kernel and
> > patched it. What kernel is ideal to use with LVM? This
> > one seems to work, but I read a reference in the list
> > archive that certain components are in 2.4. Is this
> > the case?
> 
> The 2.4.X kernel contains base LVM support, but you'll need
> to supplement that with patches at the same level as the
> LVM user-level tools.  Current release is 0.9.1b7.

FYI: You can get the actual GNU LVM code at www.sistina.com/lvm.

> 
> > I also read an older thread on an X11 GUI as well as
> > some replies to it. The GUI that comes with Veritas is
> > completely useless and the command line tools are
> > completely over-engineered. While it would be nice for
> > a small company trying to save money not to call in a
> > specialist to create VG's, it certainly wouldn't be a
> > requirement. Get everything stable, reliable and
> > consistent than someone will probably have the time to
> > create the GUI. I'd dedicate time to that type of
> > project, but why bother when the code isn't quite
> > there yet. There's no reason.
> 
> LVM is so simple that, IMHO, a GUI shouldn't be an overriding
> concern.  Then again, I've been working with LVM on HP-UX
> for many years, and I find the CLI utilities to be much
> more efficient than waiting for SAM (the HP-UX sysadmin
> GUI) to poll everything, build displays, etc.  The current
> CLI tools are lean and aligned with the LVM model in a
> way that is both logical and easy to understand.

Thanks for the flowers :-)

Actually there are GUI contributions out there.
For eg. http://www.xs4all.nl/~mmj/lvm/ is worth trying in order to have
the day by day LVM work items covered.

BTW: Evan is touching another major point here, which people tend to forget
easily IMHO; in critical operating situations where you are limited to
the command line (single user) you *need* to be familiar with the CLI in order
to get back to regular operation as fast as possible!

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-- 

Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

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Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
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Mauelshagen at Sistina.com                           +49 2626 141200
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