[ale] Fileserver/filesystem replication

[Christopher Fowler]

On Wed, 2003-12-31 at 04:13, Bob Toxen wrote:
> Ya want real-time replication.  I'll give ya real-time replication.
> 
> 1. Build your ext3 or ReiserFS on top of Linux software mirroring.
> 2. Make the second (mirror) disk a network disk device.
> 3. Ensure that writes are not acknowledged until they percolate through
>    to the remote real hard disk.

Is #3 done with the raid utils?

> 
> Done.
> 
> Not only do you get true real-time remote mirroring BUT with any decent
> DB your transactions will be consistent in the event of failover.
> 
> Bob Toxen
> bob at verysecurelinux.com               [Please use for email to me]
> http://www.verysecurelinux.com        [Network&Linux/Unix security consulting]
> http://www.realworldlinuxsecurity.com [My book:"Real World Linux Security 2/e"]
> Quality Linux & UNIX security and SysAdmin & software consulting since 1990.
> 
> "Microsoft: Unsafe at any clock speed!"
>    -- Bob Toxen 10/03/2002
> 
> > On Tue, Dec 30, 2003 at 10:06:20AM -0500, Matt Smith wrote:
> > Does anyone have experience with any filesystem replication methods
> > other than rsync alone?  I'm looking for something a little more real-time
> > (preferably not scheduled) to do at a minimum a one-way replication to a
> > "backup" server, and ideally, a two-way replication so that two servers
> > could be used in parallel.
> 
> > I realize the former could be accomplished with a frequently scheduled
> > rsync, but I'm hoping for something a little more robust than that.
> > I can tolerate a one-way copy to the backup server as long as it's done
> > very quickly after a file is modified, because if I ever have to fail
> > over to the backup server for reads, it probably means the primary is down
> > hard so I won't have to worry about copying updates to it any time soon.
> > I'm handling the failover via a NFS connection through a F5 Load balancer
> > that will point the connections to the primary server unless it's down...
> 
> > I've looked into coda, several clustering filesystems: pvfs, and a few
> > others (some commercial, but I've got no budget for this, of course),
> > but they all seem to either lack the nonscheduled replication I'm looking
> > for, or are more focused on parallel access than replication for fault
> > tolerance.
> 
> > Thanks in advance for any feedback on your experiences.
> 
> > --Matt
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