[Gluster-devel] Migration from Unify to DHT

Markus Gerstner m.gerstner at bmiag.de
Wed Jun 3 12:39:33 UTC 2009


has this migration document been posted already? I tried finding it on the 
wiki but wasn't successful so far. Is it enough to just use distribute with 
"option lookup-unhashed yes"?
Am I right in thinking that the client would then hash a given filename, try 
to find it on the mapped server and if that fails, ask all other servers if 
they have the given filename in their storage?
Given that neither server nor client store any metadata for DHT, this would 
mean that you can never disable this option if there are any files present 
which have not been stored using distribute, correct?

"*  lookup-unhashed
This option when provided, will make the dht translator act as a generic 
cluster translator where it sends lookup call on all the subvolumes, hence 
there will be no files missing over filesystem."
kind of sounds like distribute always sends lookups to all nodes, without even 
trying to hash first, hence the questions.

Also, is there any ETA on schedulers for DHT?

Best regards and thanks in advance,

> -----Original Message-----
> From: gluster-devel-bounces+m.gerstner=bmiag.de at nongnu.org
> [mailto:gluster-devel-bounces+m.gerstner=bmiag.de at nongnu.org] On Behalf
> Of Anand Avati
> Sent: Wednesday, December 10, 2008 6:53 AM
> To: NovA
> Cc: GlusterFS Devel
> Subject: Re: [Gluster-devel] Migration from Unify to DHT
> we will be putting up a migration document (from unify) on the wiki in
> the DHT section.
> avati
> 2008/11/17 NovA <av.nova at gmail.com>:
> > Hello everybody!
> >
> > As 1.4 release is approaching I'm preparing migration from 1.3. I hope
> > that DHT could increase performance a lot for our 24-nodes computing
> > cluster. Now unify really slows down file IO if there are hundreds of
> > files in a dir...
> > What is the simplest way for switching from unify to DHT? As I
> > understand, ideally one should recreate glusterfs volumes from scratch
> > to initialize new DHT file scheduling. But it could be problematic in
> > our case... What will happen if I start new glusterFS with DHT over
> > existing backends with thousands of files distributed by unify? Can it
> > reschedule files during self-healing process or something like that?
> > Or will it just stuck or even corrupt data?
> >
> > Thanks in advance for any comments.
> >
> > Best regards,
> >  Andrey
> >
> >
> > _______________________________________________
> > Gluster-devel mailing list
> > Gluster-devel at nongnu.org
> > http://lists.nongnu.org/mailman/listinfo/gluster-devel
> >
> _______________________________________________
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