[gentoo-user] Recovering RAID1 after disk failure

[Mike Diehl <mdiehl@diehlnet.com>]

Hi all,

I've got a sw RAID1 that just had a failed drive replaced with an identical 
drive.

However, the good drive started on sector 63 and the new drive want's to start 
on sector 2048.  Fdisk won't let me create the partition table on the new 
drive as it is on the old drive.

This is the good drive in the RAID:
===============================================
Disk /dev/sdb: 320.1 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders, total 625142448 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xfc32270f

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1              63      224909      112423+  fd  Linux raid autodetect
/dev/sdb2          224910    50572619    25173855   82  Linux swap / Solaris
/dev/sdb3        50572620   625137344   287282362+  fd  Linux raid autodetect
===============================================

However, after zero'ing out the new drive, this is what fdisk allows me to do:


===============================================
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF 
disklabel
Building a new DOS disklabel with disk identifier 0xfcd585e4.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.

Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4, default 1): 1
First sector (2048-625142447, default 2048):
===============================================

As you can see, I can't mirror the previous partitioning scheme and I will 
probably not have enough space on the new drive to build the RAID!

What can I do?



-- 

Take care and have fun,
Mike Diehl.