Re: [9fans] now for something completely devfs :)

[Fco.J.Ballesteros <nemo@plan9.escet.urjc.es>]

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I did setup the mirror before formatting venti/fossil partitions.

Otherwise, you'd need to copy one disk to another while the partitions
are idle.

Let's say you have /dev/fs/mirror out of /dev/sdC0/part and /dev/sdC1/part

If you add /dev/sdD0/part you could dd from either /dev/fs/mirror or
from /dev/sdC[01]/part to /dev/sdD0/part. You should also add the device
to devfs.

I can help somehow, let me know.

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From: andrey mirtchovski <mirtchov@cpsc.ucalgary.ca>
To: 9fans@cse.psu.edu
Subject: [9fans] now for something completely devfs :)
Date: Wed, 9 Jul 2003 09:42:02 -0600 (MDT)
Message-ID: <Pine.LNX.4.44.0307090906010.8112-100000@fbsd.cpsc.ucalgary.ca>

Now I have a venti, I'm keeping score, emailing it to myself every morning
(thanx to nemo's suggestions!) and am ready to embark on something that'll
break the machine completely! I decide to create a devfs mirror.

The fossil installation page on the wiki gives some instructions, but the
main part is missing -- how to write the first disk to the second one?

In the hardware RAID world, there are utilities provided for copying a hard
drive 'en masse' to others to create the mirror. With devfs I'm supposed to
do it myself.

But what do I copy? The entire drive (dd -if /dev/sdC0/data -of /dev/sdD0/data)?
Partition by partition? The wiki says:

	If you already have a fossil and want to add another disk to
	mirror it, you can setup the mirror as said before, start your
	fossil and while you are using it, use dd(1) to copy the first
	device to the new one. Since writes go to all devices but reads
	are performed just by the first device as long as it works it
	can be done this way.

but what does 'other one' mean here? am I supposed to do something like:

	dd -if /dev/sdC0/isect -of /dev/fs/isect

? (ok, I try that -- I echo a file to sdD0's isect, run the command, it
takes much longer than normal, completes, I run cmp on the two drives
-- they're not the same.)

Another thing: I should *not*, repeat *not* mirror 9fat with devfs, right?
Because if I do the machine becomes unbootable. MBR... shows up, but 9load
is nowhere to be found.

also: how do I know if one of my /dev/fs/ mirrored disks has crashed? I
mean, without rebooting :)

andrey