Unforgiving Software Raid (2.4.20)

[Matthew Carpenter]

On Wednesday 02 November 2005 02:12, Roger Oberholtzer wrote:
> > BOTTOM-LINE:  I need to take back my rants against LVM and RAID as they
> > are unsupported at this point.  That doesn't mean they aren't true, just
> > that I'm no longer convinced.
>
> For me, good news. For you, more coffee and, perhaps a whiskey.


:)  Still drinkin'.  So far the box has been stable.  I still have one drive 
out of the mix, but the production drives are in RAID fashion and have been 
stable.

And I skipped the "LVM -> RAID only" conversion.  I figured it would change 
too many variables.  Since this is a "product" not just some random box, I 
have history and support to consider.  Let's keep this puppy the same for 
now.

And to clarify, that was "Two LVs on RAID" being converted to "Two RAID 
arrays".  I'm not sure BigBlock version 2 will ship with LVM by default.  It 
will have to support it for upgrades, but I'm not sure about new systems...  
I've just mocked up a VM to play with.  I'll add create an array, then break 
it, and then see if LVM chokes.  Viva VMware!

And to further attest to my own stupidity and the affects of stress on my 
logic ability....  I was building LVM and RAID on 2.6 and then expecting 2.4 
kernels to understand them.  I'll own up to it...  not very smart.
>
> > However, I will offer this rant:
> > LVM and RAID between different versions are anything but friendly.  eg. 
> > This is a SuSE 8.2 box, running 2.4.20.  When I booted off the SuSE9.0
> > and 9.1 and Ubuntu cd's I was able to create everything just how I wanted
> > it.  But I had a difficult time getting any of the others to read the
> > drive.  I can understand not going from 2.6 to 2.4, but between the
> > different 2.6 kernels you might think things work.  I suppose this is all
> > based on little experience, but it's been a painful learning process. 
> > Temper that with the fact that in the past 36 hours I have had 2 hours
> > sleep, 2 hours of trick-or-treating, and 30 hours of work.  I'll be the
> > first to tell you that I'm not exactly balanced at the  moment.  Please
> > forgive the ranting.  I'm beat.
>
> This has been a concern of mine. I think I posted a question along these
> lines back in the mists of time. Never did get a straight answer. The
> main reason I was considering hardware RAID1 is that I would remove that
> variable when going to a new release. Of course, then I may need to lay
> in a few spare RAID1 controllers in case one dies. I assume that all
> RAID1 disks are not interchangeable between the various RAID1
> controllers. Then 'only' the LVM compatibility would be needed. Not that
> and RAID1 as well.

Yup.  but let me just say this:  Linux LVM and RAID still rock.  I 
particularly like them since they show up the same regardless of BIOS 
inconsistencies.  Recently I have had to deal with several hardware configs 
which treat hard drives differently.  One machine shows the first HD 
as /dev/hda, another /dev/hdc (laptop where cdrom appears first for some 
reason), and yet another /dev/hdi
So long as GRUB can find the kernel and initrd, it scans for the PV/VG/LV 
stack and /dev/md0 is /dev/md0.

Have fun all.

-- 
Matthew Carpenter 
matt at eisgr.com                          http://www.eisgr.com/

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