LinuxSA Mailing list archives

  From: Adrian Butterworth <adrian@econ-outlook.com.au>
  To  : linuxsa@linuxsa.org.au
  Date: Sat, 15 May 1999 19:41:14 +0930

Re: Mirror Systems

Tim
I note no-one has replied yet, so -
1. IDE RAID-1 mirroring is not expensive
2. Less glam but industrially effective for periodic mirroring
   (say every 10min or every hour or every day) to a second disk on same machine
   script + rsync (disk to disk)
3. for periodic mirroring to a second system use (better to suck than push)
   a. script + NFS + rsync(your missing ingredient)
   b. or for a secure transfer script + ssh + rsync

I use 2, 3a and 3b in different sites each has its uses
(I am in the process of experimenting with 1) 

Tips: 
1. if you use cron to launch scripts use a lock to avoid race conditions caused
   by cron starting another copy before the previous has finished. 
2. to improve efficiency of the rsync. On the frequent intervals don't rsync the
   directories that don't often change like /etc /bin /sbin ... or
   where the changes are not critical like .../squid/ (do these say once a
   day at night) or are unimportant like /tmp or are- only those that are
   important  eg /home/ and /var/spool/mail ...
3. use the automount demon for nfs rather than mounting in the scripts
   this avoids timeout/lockup problems and clashes with other mount attempts

regards
Adrian Butterworth

On Wed, 12 May 1999, Timothy Aslat wrote:
> Does anyone know a way that I can mirror a linux server to an identical
> machine which will be able to take over in the event that the primary
> fails?
> I need it to update the data on the backup machine constantly 
> (I know RAID does this but I can't justify the expense at the moment)
> 
> I was experimenting using NFS and a script but it was rather slow and
> cumbersome.
> 
> Any ideas would be appreciated.
> 
> 
> Cheers
> 
> Tim

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