ZODB/ZSS High Availablity, was: RE: [Zope] Zope Myths?

[Oliver Bleutgen]

sean.upton@uniontrib.com wrote:
> Thought about this using Intermezzo - basically the same idea.   I think the
> problem is that these are on-demand replication mechanisms that get the file
> when they need it instead of push-to-other-node-on-write sort of deals. I'm
> not posive about that.  The other problem is how these filesystems handle
> changes to large files (like FileStorage). 
> 
> There, might, in theory, be a way to integrate this with something like
> DirectoryStorage, but I think you would need to do some heavy scripting to
> get things to work just right (perhaps to the point that you might as well
> manually set up scripts to low-tech replicate files?).


Hmm, has someone taken a look a ndb (network block device) for linux?
This might be a cheap (low tech) solution for doing 
"push-to-other-node-on-write". I'm asking, because I have not tried it, 
but always wanted to.

http://nbd.sourceforge.net/

http://www.it.uc3m.es/~ptb/nbd/


"""The intended use is for RAID over the net. You can make an NBD device 
part of a RAID mirror in order to get real time mirroring to a distant 
(and safe!) backup. To make it clear: start up an NBD connection to a 
distant ENBD server, and use its local device (probably /dev/nda) where 
you would normally use a local partition in a RAID setup.

The original kernel device has been hardened in many ways: The ENBD uses 
block-journaled multichannel communications; there is internal failover 
and automatic balancing between the channels; the client and server 
daemons restart, authenticate and reconnect after dying or loss of 
contact; the code can be compiled to take the networking transparantly 
over SSL channels (see the Makefile for the compilation options).
"""


cheers,
oliver