[Gllug] best way of making backups

Alain Williams addw at phcomp.co.uk
Sun Sep 14 13:19:44 UTC 2008

On Sun, Sep 14, 2008 at 01:51:15PM +0100, t.clarke wrote:
> I guess you may have seen lots of better suggestions already.
> My personal preference is to keep things dead simple:
> 1) buy a suitable size spare hard disc  (they are cheap these days!)
> 2) keep all your valuable data that you want to backup up in separate
> filesystems from all the o-s stuff which you can always download in the
> event of a catastrophe
> 3) create copy filesystems of those filesystems on your spare disc
> 4) do a daily overnight 'rsync' or 'ssync' to the backup filesystems

I was glad of my precautions y/day morning ...
You may recall that about 6 weeks ago the hard disk started giving errors on my main
home machine. It was still usable, but X did not work because of corrup .so files, etc.
The hard disk was installed some 6 years ago and the m/c is never switched off.

I wasn't too worried about data loss since I do nightly incremental backups to
another hard disk & occasional (=~ monthly) copies of these to a USB disk
that lives with a neighbour.

I decided to rebuild onto my test m/c and upgrade CentOS 4 -> 5; 32 -> 64 bit.
I put in 2 off 1TB disks that I mirrored (mdadm) and used the existing 750GB
disk for nightly backups.

It took a few days (any OS upgrade on a moderately customised m/c does) and the only
thing that does not work is flash (I've not been able to get the 32 bit wrapper to work),
probs with some perl module versioning between CentOS/RedHat & Dag's archive.
I installed under Xen & it works with the install xen kernel (2.6.18-8) but
not the latest (2.6.18-92) ... to be thought about.

The Crunch
Anyway: y/day morning one of the new 1TB disks failed. I had to force a reboot
and remove the bad disk with mdadm. I installed a new 1 TB disk (#89) & brought
it back into the mirror.

How glad I was that I did the mirroring, having to do another rebuild would
have been nasty.

I am somewhat puzzled that the mirroring did not discard the bad disk automatically
and so forced me to reboot.


Disks are not expensive any more: use mirroring.

Alain Williams
Linux Consultant - Mail systems, Web sites, Networking, Programmer, IT Lecturer.
+44 (0) 787 668 0256  http://www.phcomp.co.uk/
Parliament Hill Computers Ltd. Registration Information: http://www.phcomp.co.uk/contact.php
Chairman of UKUUG: http://www.ukuug.org/
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