Hi Jens,
On 25/11/08 17:20, Jensen, J (Jens) wrote:
> I understood "xroot" and "xrootd" were considered synonymous, rather
> than as you'd expect xrootd being the daemon specifically. Been a while
OK, I checked (again) and xrootd is the protocol but people (including
the developers) do also use xroot. The suite of software that first used
this protocol is called Scalla (Scalable Cluster Architecture for Low
Latency Access) which is composed of an xrootd file server and an olbd
clustering server (not a requirement - can work without this). The
xrootd server was originally developed within the ROOT analysis
framework to serve ROOT files (the format that the physics data is
stored in). xrootd is something of a successor to the rootd (or root)
protocol.
The point of the Scalla system is to provide low latency access to files
on disk such that you can run very efficient analysis jobs.
http://xrootd.slac.stanford.edu/papers/Scalla-Intro.htm
> I believe people _are_ thinking about using xroot between sites for SRMs
> that both support it, but only in the v-e-r-y long term. Would require
> improved security in xrootd though but I understand there have been a
> slew of improvements recently (at least for CASTOR). Security is
> managed via plugins I believe (but again haven't looked at it for a while).
Which people? Maybe xrootd does have advantages over gridftp.
Yep, it uses plugins. Currently, GSI, Kerberos IV and V, as well as
simple password authentication are supported.
> In the shorter term, we actually do have the DPM clients installed on
> the UI at RAL. Causes no end of confusion with RFIO. I have started
> using ROOT for testing though, and ROOT can also do xrootd. Looking at
> interoperation would be good if it's a problem but it's not exactly a
> showstopper at the moment. I think if we're to start running secure
> xrootds then getting the security consistent would be a good start.
At Edinburgh I just softlink libshift.so to libdpm.so. The ROOT
framework always looks for libshift, so this approach means that when I
try to access a file using rfio://, the ROOT loads libshift which in
fact is loading libdpm, so there are no problems with accessing the data.
Greig
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