[linux-lvm] MD RAID DEVICES INFO

[Andi Kleen]

On Thu, Feb 24, 2000 at 05:33:52PM +0000, A James Lewis wrote:
> 
> Ah,
> 
> It becomes clear, I was worried that there was major duplication of effort
> going on and that LVM was implimenting the MD functionality....
> 
> It seems logical that MD provide the underlying redundnancya nd LVM
> provide volume management... 
> 
> Do I assume that MD will be available in 2.3/2.4 eventually..... it
> sounded from the original post that it was going to die....

The original poster was clearly misguided, there are no signs of MD dying
in 2.3/2.4. Some functionality from MD 0.90 has not been merged yet (RAID5),
because it requires some more infrastructure changes in 2.3.x, but that
will hopefully be solved before 2.4. 


-Andi

> 
> On Thu, 24 Feb 2000, Heinz Mauelshagen wrote:
> 
> > > 
> > > The MD functionality has only just matured, how is this to be moved
> > > forward into 2.4?
> > 
> > Today there's MD concat and RAID0 only in 2.3.x.
> > 
> > > Is the MD functionality being rolled into LVM?
> > 
> > No.
> > 
> > I don't like to create moster ;-{)
> > A modular approach is better by far (see below).
> > 
> > > What
> > > about duplication of effort.... I take it that large portions of code can
> > > be shared?
> > 
> > No. It's not a question of large portions of code.
> > Basically supporting RAID0 in LVM is fairly simple and gives
> > you the choice for performance on which lower layer software
> > or hardware solution..
> > 
> > > 
> > > I am told that LVM supports only linear and RAID0 which is hardly
> > > useful...
> > 
> > This is a misleading statement.
> > 
> > Actually it's a question of how to layer several functional parts
> > on each other.
> > LVM basically gives you the flexibility of online resizing everything.
> > 
> > MD is the software solution which can be stacked below LVM to enable
> > software RAID1/4/5.
> > 
> > OTOH you are able to use dedicated hardware RAID subsystems instead
> > which are easier to administer and LVM on top of them to get the flexibility
> > to resize.
> > 
> > IOW: MD is one solution to address disk subsystem redundancy,
> >      hardware RAID subsystems is another.
> >      Volume Management sits on top of one of these
> >      (or even on mixed configurations).
> >      It can sit on top of multiple non redundant disks as well.
> > 
> > > I appreciate that this is a work in progress but with 2.4 on the
> > > horizon can we really justify dropping a well tested and functional system
> > > for somthing without the major functionality of MD?
> > 
> > Nobody wants to drop MD AFAIK!
> > 
> > Heinz
> > 
> > > 
> > > Perhaps somone can let me know how they see this moving forward?
> > > 
> > > On Thu, 24 Feb 2000, Michael Loftis wrote:
> > > 
> > > > MD has been unsupported since the 2.2 series of kernels (it wasn't
> > > > marked as such because nobody realised this until the 2.2.13->2.2.14
> > > > patch.
> > > > 
> > > > Since everyone has been asking about it I figured I'd let everyone know.
> > > > 
> > > > If someone wants to pick it up drop by l-k and check and see if anyone
> > > > ahs yet.
> > > > 
> > > > --
> > > > Michael Loftis
> > > > zop12 at mindless.com   ICQ: 15648280  AIM: DyJailBait
> > > > Funny quip of the moment just happens to be....
> > > > Linux is like a tent:
> > > > no gates, no windows, and an Apache inside!
> > > > 
> > > > 
> > > 
> > 
> > 
> > -- 
> > 
> > =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> > 
> > Systemmanagement CS-TS                           T-Nova
> >                                                  Entwicklungszentrum Darmstadt
> > Heinz Mauelshagen                                Otto-Roehm-Strasse 71c
> > Senior Systems Engineer                          Postfach 10 05 41
> >                                                  64205 Darmstadt
> > mge at EZ-Darmstadt.Telekom.de                      Germany
> >                                                  +49 6151 886-425
> >                                                           FAX-386
> > =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> > 
>