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Feedback from dCache team
As it happens, we've been trying to forge some connection with the Globus team.
I can give a quick update ("brain dump") from a recent meeting with Vas Vasiliadis.
Globus provide software: GCS (Globus Connect Server) that sites deploy to provide access to their storage. Globus is currently transitioning between two versions: GCSv4 and GCSv5.
The GCSv4 software is (for data transfer purposes) a GridFTP endpoint. It listening on port 2811 with the control channel using GSI encoding, uses X.509 client authentication. The data channels use MODE E.
The Globus Toolkit (and its successor in GCT) GridFTP server is compatible with GCSv4. dCache is also compatible with GCSv4. Both dCache and GT/GCT GridFTP servers are currently in use as Globus endpoints.
Globus say that the GCSv5 software still uses GridFTP, but the control channel listens on port 443. It also uses token-based authentication, (rather than X.509). The encoding of the control channel has also changed. Vas mentioned HTTP, but he was light on details. The data channel still uses TCP connections with MODE E.
The Globus central server is compatible with GCSv4 and GCSv5 endpoints; for example, a Globus user can directly manage (e.g., create directories, delete files) GCSv4 endpoints and GCSv5 endpoints. The central server can also initiate transfers between two GCSv4 endpoints, between two GCSv5 endpoints, and between a GCSv4 endpoint and a GCSv5 endpoint. This last option comes from both versions supporting the same data channel.
My impression is that many (most?) Globus sites still have GCSv4 deployed.
Globus are working in improving the upgrade process, automating it. They expect to have this completed by this summer -- or the end of this year at the latest. Once the upgrade is tested, they will push sites to upgrade. Once sites have upgraded they intend to drop support for GCSv4. The timescale for this last step is unclear.
dCache's GridFTP implementation is *not* dependant on Globus Toolkit (or GCT), it's an independent implementation. Therefore, dCache is unaffected by Globus dropping support for GT.
Therefore, I am interested in learning more details about the GCSv5 control channel. This is to learn what would be required to make dCache compatible with a GCSv5 endpoint -- this could be relatively easy to implement.
To be clear: dCache has not ruled out updating dCache to support the new GCSv5 protocol, but we're also far from convinced this is the correct way for us to proceed.
We are NOT volunteering to implement GCSv5, but will work on it if WLCG sees it as a strategic direction.
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