File system replication between servers

Marc G. Fournier scrappy at
Sat Sep 4 19:24:13 PDT 2004

On Sat, 4 Sep 2004, Dan Nelson wrote:

> In the last episode (Sep 04), Marc G. Fournier said:
>> Does anyone know of any software that will run on FreeBSD that would
>> allow you to keep two servers in sync?  All writes to /dir1 on
>> server1 would go to /dir1 on server2, and all writes to /dir2 on
>> server2 would go to /dir2 on server1?
>> I've thought about rsync, but am trying to get it as close to real
>> time as I can, and on large file systems, rsync would just get too
>> far behind, too quickly ...
>> I've started to look at Coda6, but so far what I'm reading through
>> the docs makes it sound like it may not be suitable ...
>> What I'm looking for is a hot failover solution using FreeBSD ... if
>> server1 goes down, server2 can start up and continue working ... when
>> server1 comes back up again, changes to server2 could be re-sync'd
>> back to server1, and server1 could once more resume its duties ...
> How about a shared SCSI drive, filesystems only mounted on the master.
> When the master fails, the slave fscks the filesystems, mounts them,
> and becomes the master.  Tried and true.  You could even use background
> fsck and get immediate failover.

need to do this above the hardware layer ... am looking at 50% of services 
running on each of 2 servers, with failover to 100% running on one of the 
servers if the other goes down ...

reading through coda's docs, I think I can do it using that, just curious 
if there is a simpler setup that could be used ...

> You could even do it without shared storage if you use geom_gate and
> geom_{mirror,vinum,ccd} to keep two identical disks on each machine in
> sync. When the master crashes and comes back up as a slave, the mirror
> code will update its disks.

what is geom_gate?  checked 'man geom_gate' on my 5.x machine, and nothing 
shows up ...

Marc G. Fournier           Hub.Org Networking Services (
Email: scrappy at           Yahoo!: yscrappy              ICQ: 7615664

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