On Wed, 2007-04-04 at 09:38 -0400, Douglas Allan Tutty wrote:
> On Wed, Apr 04, 2007 at 08:55:55PM +0800, Wei Chen wrote:
> > 1) How does LVM handle power/disk faults?
>
> Think layers. A logical volume is made up of one or more physical
> volumes.
Well, I hate to correct you. In LVM there three^Wfour core elements:
* PV == Physical Volume or some kind of media usable by LVM, these
have Physical Extents on them.
* VG == Volume Group which is measure in two ways, Extents and
PVs. Logical Extents are the measure in which VGs use the PVs.
PVs can be added or removed, therefore adding or removing
Physical Extents. Logical Extents can be 1:1, or 1:X
* LV == Logical Volume, this is the piece typically used with
filesystems on them. Depending on *Policy* or creation
restrictions, you can have a simple "gobs of disk space", using
a 1:1 ratio for LE to PE. Or you can simply create a policy to
have LE == 2 or more PE. The in effect mirrors the Extents on
separate PVs, eliminating the problems you are talking about.
> The filesystem sees the logical volume as just another block
> device. If the power fails its no different with LVM as with plain
> disks; it depends on your file system.
Yes that is pretty much all correct, it is not JUST another block
device... it can be redundant or very fragile, depending on your
allocation policy.
> Ditto drive failures; if one drive (PV) fails then plan on losing the
> whole LV.
Not needlessly so, redundancy is available and used in LVM.
> Power failures are why I use JFS. There have been plenty of thread on
> that topic recently.
Many journaled filesystems are good about that. Some though have proven
to be troublesome i.e. Reiserfs v3.5 or v3.6. I know this from multiple
experiences. It isn't just me, either.
> > 2) Is there any Debian specific LVM Howtos where I can learn
> debianized LVM?
> >
>
> Not that I've seen, but the commands are the same as the standard
> HOWTO.
LVM is the same on really any Linux distro. Heck it even works like the
IBM LVM in AIX, though fewer options, because IBM is all about really
keeping data and haven't invested the time and effort into it for Linux,
yet.
> > 3) How does LVM handle software upgrades in Debian?
>
> Like Debian always does: It Just Works (TM)
Yup. Ditto.
[much snippage]
> Enjoy.
You are free to do it any way you want. I do it differently, but then,
everyone does it differently. There is no single "right way". Guidelines
perhaps (as you gave) but guidelines they are.
--
greg, [EMAIL PROTECTED]
Life moves on, whether we act as cowards or heroes. Life has no other
discipline to impose, if we would but realize it, than to accept life
unquestioningly. Everything we shut our eyes to, everything we run away
from, everything we deny, denigrate or despise, serves to defeat us in
the end. What seems nasty, painful, evil, can become a source of beauty,
joy and strength, if faced with an open mind. Every moment is a golden
one for him who has the vision to recognize it as such.
Henry Miller
--
To UNSUBSCRIBE, email to [EMAIL PROTECTED]
with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
