Re: LVM Documentation
- From: "icculus" <jameswadams55@xxxxxxxxxxx>
- Date: 30 Jan 2006 19:35:26 -0800
JohnK wrote:
>
> Hi icculus, what were you trying to do with your disk? What were the
> 'alterations'? If you just wanted to replace it you could have done a
> vgcfgbackup beforehand and then restored the VG setup back to the
> replacement volume with vgcfgrestore and then re-synced.
> I've worked with LVM for a few years now and haven't really found it to
> be limiting in any way. It is much more straightforward and flexible
> (to me) than Solaris disksuite e.g.
Well, DiskSuite isn't really intended to do quite as much as HP-UX LVM.
In any event, I'm not sure it made sense for HP to self-virtualize the
root
just to prove it could be done. I've had the argument for a decade
with HP
that mirroring the boot drives should be done in hardware, because the
only
functionality that makes sense is to mirror the drive, not the
individual volumes.
Indeed, this is the case in almost all HA environments. Very few
people ever
mirror anything except to gain availability, and that inevitably
applies to hardware.
If you want improved read performance, you probably want better
hardware anyway.
It seems kind of silly to have the first three contiguous partitions on
a disk LVM
when you can't do anything with them that you can't do with a
traditional hard
partition. All it does is to make systems administration more
convoluted by
introducing a useless level of indirection.
However, this discussion is getting far off track from my original
posting. I am
not a HP-UX newbie. Indeed, I had access to a source license for 9.xx
and had
internal access later on. The modifications I wanted to perform
involved some
significant changes to the root volume group on newly (mis) installed
servers.
It's a sordid tale, but the point is that I wasn't able to be there to
install the OS
the way I wanted, and I wanted to change it with minimal effort in an
environment
where there was not yet any functional network and the servers had no
local
tape drives. In other words, an enterprise environment. BTW, when I
say no
network, that also includes the planned FC SAN.
In any event, I was eventually able to resolve the issue with help from
HP support
without having to reinstall everything but I am not comfortable with
this "special
sauce" approach to systems administration. In other words, what the
support
consultant told me to do "worked," but I don't have any documentation
to tell me
why it worked or whether it might work on the next release. Indeed, it
seemed
kind of scary in assuming that LVM would figure out how to do the right
things.
Either LVM is a lot smarter than we have been led to believe or else I
have
witnessed a miracle, and as an experienced sysadmin, I don't believe in
miracles.
This still doesn't answer my question, though. MirrorDisk-UX is with
us for the forseeable
future, and I want to know how to manipulate it as *I* want, not just
in a few ways
that some HP developer *assumed* I would want. After all, whose
computer is it anyway?
There's a third party manual out on the 'net which purports to be from
a course in HP-UX
"LVM Internals," a course HP doesn't openly offer, yet the "free
downloads" (DRM .pdfs
that you can't even print) look like nothing but a less comprehensive
rehash of the HP
document I posted the link to here. Additionally, the price is over
$900 US which seems
utterly absurd.
Until HP wises up and puts hardware RAID1 disk controllers in all of
their servers for the
boot drives, we'll have to struggle with their silly notions of HA.
The amazing thing is that
it's an option in their low-end HP9000 servers, but not in the mid to
high end ones unless
you choose to boot off an EVA or XP array which opens a whole other can
of worms with
respect to the chicken and the egg.
Maybe while they're at it, they'll also figure out that it might be
good to provide a memory
subsystem that can support more than half the configurable number of
CPUs without
being starved for bandwidth.
BTW, Solaris DiskSuite isn't as flexible as HP-UX LVM, but it's a heck
of a lot easier to
do commonly useful things with it once you get the hang of it and
figure out the obscure
metadata stuff. I once cloned the OS and software install for a whole
rack full of Sun
SPARC Solaris servers in less time than it would take to begin to
figure out how to
set up an Ignite-UX server (though I have done that in the past and it
was great for
cloning hundreds of workstations, it was almost more trouble than it
was worth for
less than a dozen servers).
HP has left their roots as an engineering company by and for engineers,
and it has
hurt them, at least at the S800 level.
.
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