Re: Replacing disk in Linux Software RAID 1

[Robin Laing <Robin.Laing@xxxxxxxxxxxxxxx>]

Michael E. Webster wrote:
> Michael,
>
> Probably - I went with "ghost" because I had a boot floppy handy.
>
> The main thing is to get the MBR from that first drive - without it,
> you're out of luck.  
>
> In software RAID, the MBR is only written to the first drive, which
> really doesn't make sense.  I would think that if you had the first
> drive fail, you should be able to boot off the second one - IMHO.
>
>
> Mike.
>
>
>
> On Fri, 2004-08-13 at 18:10, Michael Mansour wrote:
>
> > Hi Michael,
> >
> > Many thanks for the below, I'll try this process
> > tonight.
> >
> > With the "Ghost", could I simply boot from a Live
> > Rescue CD and use something like:
> >
> > # dd if=/dev/hdg of=/dev/hde
> >
> > where /dev/hde would be the new blank drive?
> >
> > Michael.
> >
> > --- "Michael E. Webster" <mwebster@xxxxxxxxxxxxxxx>
> > wrote: 
> >
> > > Michael, 
> > >
> > > Whaddaya know..  I just happen to have a recipe for
> > > doing this.
> > > I went through a similar problem about two months
> > > ago.
> > > Just substitute /dev/hde and /def/hdg where
> > > applicable.
> > >
> > >
> > > Copy the MBR to /dev/hdc (done before procedure)
> > >
> > > prompt# grub
> > >
> > > Grub> device (hd0) /dev/hdc
> > >
> > > Grub> root (hd0,0)
> > >
> > > Grub> setup (hd0)
> > >
> > >
> > > Make sure that we have the partition table for all
> > > drives backed up
> > > (done before)
> > >
> > > prompt# sfdisk -d /dev/hda >
> > > /raidinfo/partitions.hda
> > >
> > > prompt# sfdisk -d /dev/hdc >
> > > /raidinfo/partitions.hdc
> > >
> > > prompt# more /proc/mdstat > /raidinfo/mdstat.md
> > >
> > >
> > > Estimated time: zero minutes
> > >
> > >
> > > Shutdown the box
> > >
> > > Remove /dev/hda and label as â??hda badâ??
> > >
> > > Boot box to make sure it boots
> > >
> > > Shutdown server and place new blank drive in ide0
> > > (new hda)
> > >
> > > Estimated time: ten minutes 
> > >
> > >
> > > Ghost ide1 (hdc) to ide0 (hda)
> > >
> > > Do â??Boot Imageâ?? copy
> > >
> > > Estimated time: a little more than an hour
> > >
> > >
> > > Remove ide1 (original hdc) and label as â??hdc
> > > goodâ??
> > >
> > > Power on to make sure ide0 (new hda) boots
> > >
> > > Shutdown and place new blank drive in ide1 (new hdc)
> > >
> > > Power on to make sure it boots
> > >
> > > Shutdown
> > >
> > > Estimated time: fifteen minutes
> > >
> > >
> > > Power on and boot
> > >
> > > Copy the MBR to hdc
> > >
> > > prompt# grub
> > >
> > > Grub> device (hd0) /dev/hda
> > >
> > > Grub> root (hd0,0)
> > >
> > >
> > >
> > > Hope this helps,
> > > Mike.
> > >
> > >
> > >
> > >
> > > On Fri, 2004-08-13 at 17:51, Michael Mansour wrote:
> > >
> > > > Hi,
> > > >
> > > > I have a server with a 2 disk Linux Software RAID
> > >
> > > 1
> > >
> > > > setup (two 80Gb disks). The first device is
> > >
> > > /dev/hde
> > >
> > > > and the second is /dev/hdg.
> > > >
> > > > The /dev/hde device is ready to fail, as it
> > >
> > > produces
> > >
> > > > various SMART errors using smartctl and fails on a
> > > > self-test with:
> > > >
> > > > [root@gazelle root]# smartctl -l selftest /dev/hde
> > > > smartctl version 5.30 Copyright (C) 2002-4 Bruce
> > >
> > > Allen
> > >
> > > > Home page is http://smartmontools.sourceforge.net/
> > > >
> > > > === START OF READ SMART DATA SECTION ===
> > > > SMART Self-test log structure revision number 1
> > > > Num  Test_Description    Status                 
> > > > Remaining  LifeTime(hours)  LBA_of_first_error
> > > > # 1  Short offline       Completed: read failure  
> > >
> > >   
> > >
> > > > 90%        34         0x0463c0ee
> > > > # 2  Short offline       Completed: read failure  
> > >
> > >   
> > >
> > > > 90%      1087         0x0425290c
> > > > # 3  Extended offline    Completed: read failure  
> > >
> > >   
> > >
> > > > 90%      1072         0x0425290c
> > > > # 4  Short offline       Completed: read failure  
> > >
> > >   
> > >
> > > > 90%      1072         0x0425290c
> > > > # 5  Short offline       Completed: read failure  
> > >
> > >   
> > >
> > > > 90%      1071         0x0425290c
> > > >
> > > > The server is running Fedora Core 1.
> > > >
> > > > I have the new 80Gb disk and wish to replace
> > >
> > > /dev/hde
> > >
> > > > device with the new disk, how do I do this?
> > > >
> > > > The following is how I have the mirror setup:
> > > >
> > > > # fdisk -l /dev/hde
> > > >
> > > > Disk /dev/hde: 80.0 GB, 80026361856 bytes
> > > > 255 heads, 63 sectors/track, 9729 cylinders
> > > > Units = cylinders of 16065 * 512 = 8225280 bytes
> > > >
> > > >   Device Boot    Start       End    Blocks   Id 
> > > > System
> > > > /dev/hde1   *         1       395   3172806    b 
> > > > Win95 FAT32
> > > > /dev/hde2           396       408    104422+  fd 
> > > > Linux raid autodetect
> > > > /dev/hde3           409      1070   5317515   fd 
> > > > Linux raid autodetect
> > > > /dev/hde4          1071      9729  69553417+   f 
> > > > Win95 Ext'd (LBA)
> > > > /dev/hde5          1071      1331   2096451   fd 
> > > > Linux raid autodetect
> > > > /dev/hde6          1332      1585   2040223+  fd 
> > > > Linux raid autodetect
> > > > /dev/hde7          1586      1716   1052226   fd 
> > > > Linux raid autodetect
> > > > /dev/hde8          1717      4327  20972826   fd 
> > > > Linux raid autodetect
> > > > /dev/hde9          4328      9729  43391533+  fd 
> > > > Linux raid autodetect
> > > >
> > > > with /dev/hdg being exactly like above.
> > > >
> > > > As soon as I pull out the /dev/hde device, the
> > >
> > > server
> > >
> > > > won't boot (as grub only resides on /dev/hde), so
> > >
> > > I
> > >
> > > > also installed grub on /dev/hdg to overcome that
> > > > problem. But now I'm wondering what I must do to
> > >
> > > pull
> > >
> > > > out /dev/hde and replace it with the new drive
> > >
> > > (which
> > >
> > > > doesn't have any partitioning setup) and then
> > >
> > > force
> > >
> > > > Linux to resync the data on /dev/hdg to the new
> > > > /dev/hde?
> > > >
> > > > Is there some way I have to fail the /dev/hde
> > >
> > > drive,
> > >
> > > > replace it then put it back on-line? First time
> > >
> > > I've
> > >
> > > > done this with Software RAID so I'm not sure.
> > > >
> > > > Any advice is appreciated.
> > > >
> > > > Michael.
> > > >
> > > >
> > > > Find local movie times and trailers on Yahoo!
> > >
> > > Movies.
> > >
> > > > http://au.movies.yahoo.com
> > >
> > >
> > > --
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> > > fedora-list@xxxxxxxxxx
> > > To unsubscribe:
> > > http://www.redhat.com/mailman/listinfo/fedora-list
> >
> > === message truncated === 
> >
> > Find local movie times and trailers on Yahoo! Movies.
> > http://au.movies.yahoo.com

Would it be possible to write the MBR to the second disk just in case?
--
Robin Laing