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Re: [Linux-cluster] Samba Technical thread



On Wed, Dec 08, 2004 at 09:48:33AM +1100, John Newbigin wrote:
> Christopher R. Hertel wrote:
:
> >Question on this.  Is there any interest in clustered block media?
> >
> >Eg., what if five systems all had access to the same chunk of (virtual)  
> >disk via iSCSI.  Is there a way that one of those five could create an
> >EXT3 filesystem on that raw block-space such that all of the five 
> >clustered systems would see an EXT3 partition (and be able to use it 
> >concurrently)?
> No (well not for a writable filesystem).  You still need a cluster 
> filesystem so you don't trash the filesystem.  I believe that work is 
> underway for a cluster raid to run gfs on top of.  This would be good 
> for people without shared storage hardware but still want to use GFS.

I imagine that it would be doable, somehow.  :)  Possibly not with GFS,
but... You would certainly need to have the cluster layer, it would
present block storage to the kernel.  I'm thinking along the lines of 
clustered iSCSI.  Dunno if that's practical, but I like the mental 
exersize.

> >Oh... and a side-comment.  CIFS tries, and gets fairly close, to copy 
> >local FS semantics.  The problem is that those semantics are DOS, OS/2, 
> >and NTFS semantics.  The protocol has support for all of these, and there 
> >are some folks who have tried to add Unix semantics as well.
> I did the initial implementation of the Unix semantics in the smbfs 
> driver.  POSIX semantics just aren't possible over CIFS.  Unlinking an 
> open file for example.  I tried for weeks to implement that in smbfs and 
> samba.  Windows does not have such a concept so it is very difficult to 
> make it work over CIFS.  This means that programs that do stupid NFS 
> locking workarounds (like gconfd) won't run with CIFS mounted home 
> directories.

Well... In the most course-grained fashion you could add a new dialect 
string to the NegProt and then run an entirely different protocol if both 
systems agree to do so.  That's not what's happening, however.  The folks 
working on this are adding new Infolevels and suchlike over and above the 
original work by Byron at HP.  I don't know how far that will go.  Sounds 
like you've got more experience there.

Thanks!

Chris -)-----

-- 
"Implementing CIFS - the Common Internet FileSystem" ISBN: 013047116X
Samba Team -- http://www.samba.org/     -)-----   Christopher R. Hertel
jCIFS Team -- http://jcifs.samba.org/   -)-----   ubiqx development, uninq.
ubiqx Team -- http://www.ubiqx.org/     -)-----   crh ubiqx mn org
OnLineBook -- http://ubiqx.org/cifs/    -)-----   crh ubiqx org


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