Re: K12OS: rsync as alternative to nis/nfs?
Eric Harrison (eharrison@mail.mesd.k12.or.us)
Tue, 12 Feb 2002 21:02:42 -0800 (PST)
On Tue, 12 Feb 2002, Dan Young wrote:
>Re: the interval for synching:
>
>If the maximum # of connections in your rsyncd.conf is set to one, you'll
>never start a session while another is running, although this obviously
>won't work if you plan to sync more than two servers.
>
>I've a wee bit of experience (emphasis on "wee bit") with the multiple rsync
>session syndrome (our web server uses this to sync between a staging and
>production server) and it gets a bit weird when sessions overlap.
>
>-Dan Young
>-Parkrose School District
>
>> The bidirectional thing turns out to be trivial - the only challenge
>> will be determining an appropriate interval - the shorter the better,
>> obviously, but there needs to be enough time to finish synching before
>> the next scheduled sync starts - trial and error will be the solution
>> here :)
Dan brings up a good point here: if you are doing bi-directional rsyncing
among multiple servers, you'll run into some weird problems with temporary
files.
Envision edge server #1 syncing TO the master server at the same time that
edge server #2 tries to sync FROM the master server. It seems like you could
quickly run into some crippling loops, especially as the number of servers
increases.
LinuxWorld recently had an article on unison, an rsync-like utility designed
for bi-directional synchronization:
http://www.linuxworld.com/ic_788354_7077_1-3135.html
Other, less hackish options include NFS replacements that deal with
disconnected use such as coda or intermezzo:
http://www.coda.cs.cmu.edu
http://www.inter-mezzo.org
-Eric
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