[tahoe-dev] server selection

Troy Benjegerdes hozer at hozed.org
Wed Apr 22 18:55:24 UTC 2009


On Wed, Apr 22, 2009 at 10:34:09AM -0600, Shawn Willden wrote:
> On Tuesday 21 April 2009 02:50:41 pm Brian Warner wrote:
> > We picked the pseudo-random permuted serverlist to get these properties.
> > I'd love to be able to get stronger diversity among hosts, racks, or data
> > centers, but I don't yet know how to get that '''and''' get the properties
> > listed above, while keeping the filecaps small.
> 
> Well, there's always the old CS aphorism:  "There is no problem in computing 
> that cannot be solved (or created) by another layer of indirection".
> 
> What about using the permuted list to find a set of servers that know the set 
> of servers that hold the shares?  The share location list deployed to the 
> first n servers in the permuted server list would be small, so it wouldn't 
> impose a large burden either on servers storing the list or on clients 
> uploading the list, and it would allow complete freedom to place shares 
> wherever the client wants them.

Would there be a reasonable way to use DNS SRV records to do this? For
example, 'username.livejournal.com' is quite a conventient way to map a
DNS name to a particular set of servers.

It's also quite convenient for distributed filesystem clients.. My
laptop looks up DNS records for my AFS and Kerberos servers. There are
also lots of nice ways to use DNS to return only the
topologically closest servers, for instance.

Let's not invent another naming abstraction if there's a reasonable one
already there ;)



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