[NTLUG:Discuss] Software RAID-1 success and questions.

[Dan Carlson]

You can use dd if=/dev/zero of=/dev/hdX to erase an entire drive.  It takes
a while on a large drive, but it works.  It should figure out the size
automatically, but if not you can add the bs and count options to tell it
how much to erase.  Frequently all you really need to erase is the
beginning and the end, which you can do a lot faster than doing the whole
drive.  Use the seek option to skip to a particular location on the output
device.

If everything is setup properly, swapping hda and hdc should work just
fine.  In my experience, the only way to know for sure if you have setup
everything properly is to try it.  Of course, this is risking data loss if
it turns out that something isn't setup properly!  With raid it is best to
take a few days and try everything out to make sure it all works the way it
is supposed to, including recovery.  The available recovery information
isn't as clear or complete as it should be, in my opinion.  Here is some
useful info, which should be consulted in addition to chapter 6 of the
Software RAID Howto:

http://www.tldp.org/FAQ/Linux-RAID-FAQ/index.html#AEN127

http://web.gnu.walfield.org/mail-archive/linux-raid/2000-June/0291.html

To have two bootable disks in the same system you can install lilo into the
mbr of each disk and use the bios to specify which disk to boot off of.
This works fine for me.  You will need two separate lilo.conf files (say,
lilo.conf.hda and lilo.conf hdc) and use the -C option to tell lilo which
config file to use.  Run lilo twice, once with each config file.  Then try
changing the boot drive in the bios.  "If everything is setup properly", it
should work.

Dan Carlson

----- Original Message -----
From: "Richard Geoffrion" <ntlug at rain.lewisville.tx.us>
To: <discuss at ntlug.org>
Sent: Thursday, June 27, 2002 9:16 AM
Subject: [NTLUG:Discuss] Software RAID-1 success and questions.


> . . .
>
> ****  Questions below ****
>
> So how does one clean information off of a superblock?  What would happen
if
> I just swaped /dev/hda and /dev/hdc?  How does one make TWO bootable IDE
> drives and have each of them boot up the same linux system?
>
> Any comments or suggestions?
>
> -Richard
>
>
>
>
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