Re: AW: [geclipse-dev] Remote-to-remote transfers with SRM

[Ariel Garcia <garcia@xxxxxxxxxx>]

Hi all,

just to clarify, in gLite

- there are Storage Elements, with storage space, one or more transfer 
protocols (gridftp, rfio...) and eventually a SRM layer to interface with 
the "native backend" DPM, dCache, etc
  [ we don't (want to) care if the backend has its own interface accessible 
via net ] The backend takes care of managing the lifetime of the files, 
cataloging the stored files in that SE, reserving space, etc. but _not_ of 
the data-transfers (writing, reading data) themselves.

- there is the file catalog LFC, which just cares about _cataloging_ the 
files in a whole (grid) set of SEs, it cannot start or doesn't take care 
in any (3rd party or direct) transfers.
[ the normal use case involves a tool in the UI who cares of uploading a 
file to a SE and immediately registering it in the LFC , or asking the LFC 
where a given data (logical file name) can be physicaly found and 
initiating a download from a SE via gridftp/rfio/... ]

- there is the FTS file transfer service which works as a "resource broker" 
for data transfer jobs, has a WS interface, and can schedule/control the 
data transfers. Of course if the FTS replicates a file from one place to 
the other, it would register the resulting replica in LFC when the tranfer 
is done.

Regarding the SE's,  gridftp and the SRM specification v2.2 support 3rd 
party transfer but as Mateusz found the SRM-layers for several of the 
backends just don't implement the 3rd-party-transfer method(s) from SRM
 --->  which doesn't mean that they won't implement it in the next 
versions! (i am optimistic today ;-)
So it would be possible to implement those parts and say "our part is 
ready" , now it is glite/Castor/dCache's job to finish their 
implementations :)

Next possibility for 3rd party transfers (higher level) means implementing 
an FTS plugin, although FTS is not so widely used and also quite Tier0/1/2 
specific  (the deployed FTS's in EGEE do not allow transfers ANY-ANY  but 
only in the preconfigured channels)

Cheers, Ariel