Subject: Re: raid-1 data offset
To: Wojciech Puchar <>
From: Greg Oster <>
List: netbsd-users
Date: 08/06/2001 09:54:22
Wojciech Puchar writes:
> what is an offset (in sectors) between beginning of partition used to make
> raid and raid data stored on it

64 sectors.

> as bootblock in 1.5.1 doesn't support RAID-1 boot 

Hmmm... It's supposed to.. (It knows to look for a FS_RAID partition)
The bigger problem is that installboot doesn't know how to deal with
RAID partitions.

> i would like to make
> "shadow" partition just for them like that on both disks:
> a: <raidsize> <e_begin+offset> 4.2BSD ....
> ..
> ..
> ..
> e: <raidsize> <e_begin> RAID .....
> f: 200       somewhere 4.2BSD
> and install bootblocks (nothing else) on f, which then will boot from a
> not knowing that it's on RAID-1

This should work, but be *VERY* careful that you don't get the RAID components 
inconsistent by modifying any data in the 'a' components without going 
through the RAID set.  If you must modify the data on 'a' directly (without 
going through RAID), then first use 'raidctl -f wd1e' (or whatever) to fail
the mirror part of the RAID set.  Once you're done mucking with 'a', then you
can use 'raidctl -R wd1e' and sync the arrays up again.  If you don't do the 
'raidctl -f' and then you change data on 'a', there is a very good chance that
you'll end up with serious filesystem corruption... but if you're careful, it
should work..


Greg Oster