[linux-lvm] LVM Questions

[Glenn Shannon]

Note: Comments interspersed in email.

Darren Young wrote:

> I have only recently discovered and played with LVM.
> If anyone can answer some general questions, it would
> be most appreciated.
>
> What I would like to have is a system where I can add
> space via new disks and expand file systems at will. I
> have used volume managers on HP and Solaris for
> precisely these purposes (HP and Veritas). Too many
> times I have been called by a customer or a customer
> of a friend with the "I underestimated the space
> needed for my Oracle databases and I need space,
> now!". Adding disks and placing db's on alternate
> filesystems gets the job done, but an LVM would be a
> great method to move them to.

Well, I just added a partition off of a 40GB drive I just acquired to my
existing LVM without a hitch.
And using reiserfs I can resize the filesystem(s) to acquire the new
space and place it where it needs to be.


> 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.

As far as I can tell I have gotten maybe a 10% increase by adding the
other hard drive (which sits on its own Promise controller) so I am not
sure at this point whether I created a pseudo-RAID 0 or not (I think
not).

That would be a great feature to have though! But with Linux already
having software raid, I don't see it becoming a priority of the
programmers to re-invent the wheel before they finish building on what
they have right now...my .02 worth.


> 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 use parted myself. FDisk is broken on my machine for some strange
reason known only to God. It keeps picking up some darned
4.2BSD partitioning schema. sfdisk and cfdisk work fine, and so does
parted.


> 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?

I am using 2.4.4 but I think I will regress back to 2.4.3 in light of
some technical difficulties I am having...but will have to wait till my
next scheduled reboot for that. I work with this stuff on a development
machine used by other people :)

By the way *they* like the changes too.....I can dynamically resize
their home partitions to accomodate their needs *without* rebooting.


> The howto mentions to add a couple of commands to the
> RH start script, but a scan of them reveals that RH
> 7.1 already has them. If they are correct, perhaps the
> howto needs to reflect this. Does anyone know if they
> are correct?

The vgscan and vgchange lines are installed by default on RedHat 7.1?
Interesting.


> I picked up on an older thread about the mailing list
> rejecting certain email and just had to dump in my .02
> worth. I don't want to start a war, but the list
> should be completely open. I remember the FreeSWAN
> list having wars over open vs closed and open won. The
> maintainers are of the opinion (from what I read) that
> filtering spam is up to the user and cleaning of any
> type of a list is censoring. I had to get that out
> since I will most likely be using this product
> somewhere down the road.

I agree. Censorship is bad when we don't do it for ourselves.


> 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.

I agree again. Good point. Although, I would like to interject my
opinion that it seems pretty darned stable right now. I can't wait to
see what these guys are going to do next!


> Guess that's a total of .04 cents...
>
> Thanks in advance,
>
> Darren Young
> Senior UNIX Administrator
> GSX.com
>
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