[OpenAFS] R/W replication

Derek Atkins warlord@MIT.EDU
13 Feb 2001 10:29:56 -0500

I doubt that RW clones will ever happen.  It would imply huge
consistency issues.  Who's job is it to make sure data is consistent
across all the servers?  In the current model, data is "pushed" from
the RW volume to the RO clones by a sysadmin (or a cron job).  You
would need more immediate data consistency with multiple RW volumes.
Worse, you also have really hard race conditions.  For example, what
if two clients are writing to the same file on different servers?  Who
wins?  How do you let the clients know that there was a conflict?

Mind if I ask to what purpose you want replicated RW volumes?  You
certainly don't need to replicate user's homedirs.  And most system
software should be RO anyways (you _do_ realize that you can still
mount the RW volume of a replicated RO volume in order to make changes
to the volume?)


Dirk Heinrichs <heinrichs@qis-systemhaus.de> writes:

> Hi *,
> comparing OpenAFS to Coda, I found that the first is only capable of
> replicating volumes read-only, while the latter can do it read-write. Is
> there any chance that this will be implemented some day?
> Bye...
> 	Dirk
> BTW: AFAIK OpenAFS and Coda share the same roots. Now that AFS is open,
> what about joining forces? Just a thought ;-)
> --=20
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       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
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