Re: RAID 1

From: Lamar Thomas (noreply_at_noreply.com)
Date: 12/28/03 

Date: Sat, 27 Dec 2003 23:41:37 -0800

Thanks for being my voice Les. I can't see any of P.T.'s posts until you
reply to them. His/Her posts just don't show up in
"comp.os.linux.networking" on my system using "Outlook Express 6.0". I am
fillowing the conversation though.

Lamar

"Les Mikesell" <lesmikesell@comcast.net> wrote in message
news:xqvHb.155107$8y1.462617@attbi_s52...
>
> "P.T. Breuer" <ptb@oboe.it.uc3m.es> wrote in message
> news:qj6lsb.fvt.ln@news.it.uc3m.es...
>
> > > The question was obvious from the first post: "when you have mirrored
> >
> > What "first post"? This is usenet!
>
> Yes, usenet messages are threaded and reasonable readers can
> traverse the list backwards to the beginning of the thread.
>
> > > partitions, how do you convince grub to make both drive's boot sectors
> > > bootable so that you can continue using the machine after the primary
> >
> > Are you sure you mean drives and not partitions? It is most unusual to
> > mirror whole drives because raid devices are not partitionable
> > themselves, and because the kernel relies on the *partition* typelabel
> > at boot to know if it is a raid device or not.
>
> That is precisely the problem. You create mirrored partitions. Update
> your kernel a few times, then the primary drive breaks. You have
> still have a copy of everything, but because grub didn't make the
> drive containing the still-working mirror partition bootable, you
> can't use it.
>
> > Perhaps you are running lvm over the raid1 device, in order to provide
> > partitions?
>
> Well, that might be a problem if Redhat's installer would actually
> install on lvm but I've never seen it work. It will install on
> mirrors but leaves the mirror unbootable.
>
> > I don't understand your question - why should you care if grub puts it
> > there or not? YOU can put it there, using the "cp" command, if grub
> > puts it anywhere at all. You will have more problem with getting grub to
> > locate the second stage loaders physical location on disk!
> >
> > So, give us a clue, what *is* your problem, exactly?
>
> As you've pointed out, it isn't simple to describe to grub how to
> make the drive containing the spare partitions bootable, and after
> going to the trouble and expense of mirroring the data it would be
> nice to be able to use it when the primary drive fails. So, that is
> the problem. Lilo seems to know enough about md devices to
> make both mirrors boot. Grub doesn't, but it has some other
> advantages and is now the default in a RedHat install. What does
> it take to make grub know as much as lilo about md partitions? Or,
> if grub can't do it, what command would you issue to make sure
> the non-primary mirror will boot.
>
> ---
> Les Mikesell
> lesmikesell@comcast.net
>
>

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