On Sat, Jul 13, 2002 at 04:23:00PM -0400, [EMAIL PROTECTED] wrote:
> I was just thinking of a way to effectively mirror content accross 
> multiple webservers in a load-sharing environment.

>     I was figuring on keeping a single FTP server for the master copy 
> and then replicating the data accross multiple machines. I'd rather 
> copy than use NFS; so there would not be a single point of failure, 
> (eg: a drive on the ftp server croakes). I was thinking of using 
> rsync; but from the way I understand it rsync just re-downloads the 
> entire tree? Could I not use CVSUP to accomplish the replication of 
> the data? As-in un a CVS server from the FTP server machine, and have 
> the webservers sync the trees they need? Any issues with using CVS and 
> image files? Or binaries alltogether? Any ideas or suggestions for a 
> better method for data replication and synchronization?

You can certainly use rsync to keep your servers in sync, and it will
use the rsync algorithm (http://rsync.samba.org/tech_report/) to
minimise the amount of data actually copied over the wire.  That means
that files which are already present on the server won't be
unnecessarily copied, even that only those chunks of a large file that
actually contain changes will be copied.

Works very well indeed, especially if you run it over ssh --- see the
FAQ at http://www.snailbook.com/faq/no-passphrase.auto.html for
details of how to secure unattended logins.

You can use cvsup in exactly the same way, but unless you've got all
your content saved into a CVS repository, cvsup will pretty much fall
back to running just like rsync.  If you are using CVS, cvsup will
look at the $Revision$ tags and pull out precisely the diff to the
latest version and apply it, which is even more efficient than rsync.
Binary file types --- images and so forth, which you can't put CVS
tags into --- can be used with a cvs repository. Remember to check-in
binary files using the `-kb' option. Binary files will always cause
cvsup to fall back to the rsync algorithm.

Other alternatives? None that I can think of better than rsync or
cvsup.

        Cheers,

        Matthew

-- 
Dr Matthew J Seaman MA, D.Phil.                       26 The Paddocks
                                                      Savill Way
Tel: +44 1628 476614                                  Marlow
Fax: +44 0870 0522645                                 Bucks., SL7 1TH UK

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