network mirroring

Michael E Brown michael_e_brown at Dell.com
Mon Aug 13 00:30:00 CDT 2001


On Sun, 12 Aug 2001, nam kim wrote:

> Hi,
> I have 2 poweredge 4400 machines.
>
> First one is Network File server, and I am thinking Second one
> will be Backup NFS.

You will need to use some specialized software to keep the servers in
sync, or you will have problems when you try to bring up the backup NFS
server. Any servers that have mounted the primary server when it goes down
will have problems with stale handles on the second server and things will
probably break badly. (short technical description: the inode numbers and
device block major #s between the two systems won't match, and the inode
number/device number is an essential link in NFS from the client machine
to which file it is using on the server)

If you can accept the fact that every machine that has mounted the primary
NFS server will most likely need to be rebooted to use the secondary
server, then "rsync" will work fine. If you don't want this, and feel you
need a more higly available solution, try:

Open Source:
drbd: 	http://sourceforge.net/projects/drbd/
	http://www.complang.tuwien.ac.at/reisner/drbd/
	http://www.linux-ha.org/  <--you probably need "heartbeat" and
"mon" as well

linuxfailsafe:	http://oss.sgi.com/projects/failsafe/

Commercial:
missioncriticallinux convolo cluster:
	http://www.missioncriticallinux.com/products/convolo

Steeleye Lifekeeper:
	http://www.steeleye.com

DRBD will give you a good low-end failover solution, especially when
coupled with heartbeat and mon. Start there and work your way up. Consider
having a specialized linux consultant come in and help if this seems too
complicated for you.
--
Michael Brown
Linux OS Development
Dell Computer Corp

>
> I want to mirror 2 directories(one /home and other is /share).
>
> Question is what's optimized way to mirror 2 directories over the
> network?
>
> OS is Redhat7.1
>
>
> Thanks
> -Nam
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