Samba and HSM

[Bryan Feir]

David Collier-Brown <David.Collier-Brown at canada.sun.com> wrote:
> Andrew Cherry wrote:
> | Files migrated to tape can take as long as 10 minutes to
> | retrieve. While attempting to access such a file, the Windows
> | NT redirector times out after about 45 seconds, and opens up 
> | a new connection (spawning a second smbd process).  
> 
> 	...
> 
> 	If not, we'll probably have to raise this on samba-technical
> 	and see if there's a way to do so. Hmmm..., or perhaps a 
> 	way to detect excessive HSM/NFS delay at read-time.

   Well, in theory that's possible on the NFS side at least.  NFSv3 has an
error code specifically for this case: NFSERR_JUKEBOX.  From RFC1813:

   The server initiated the request, but was not able to complete it in a
   timely fashion. The client should wait and then try the request with a
   new RPC transaction ID.  For example, this error should be returned from
   a server that supports hierarchical storage and receives a request to
   process a file that has been migrated.  In this case, the server should
   start the immigration process and respond to client with this error.

The proposed NFSv4 has a nearly identical code called NFS4ERR_DELAY.

   So as long as both the NFS client and server fully support NFSv3/4, the
client can find out when the HSM server is trying to locate a file.  Now, of
course, getting that information to a userland program like Samba is another
matter entirely...

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Bryan Feir           VA3GBF|"A wrangle is the disinclination of two boarders to
Work:bryan at sgl.crestech.ca | each other that meet together but are not in the
Home:jenora at sympatico.ca   | same line."              -- Stephen Leacock
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