Hi Andy, Andrew Hanushevsky wrote: > Hi Fons, > > > On Sat, 5 Mar 2005, Fons Rademakers wrote: > > >> the old rootd never allowed two or more clients to open the same file >>for writing. We have the following rules: >> >>A file can only be opened for writing if the file is not already open for >>reading or writing by any other process. >>A file can only be opened for reading if the file is not already open for >>writing (where writing of course includes "update" mode in ROOT parlance). > > That's exactly the semantic that is in xrootd. > > >>To be a full drop in replacement xrootd must be able to support the file >>update mode. I think this could be easily achieved if we allow r/w pools >>where the olbd never will trigger a replication. In such a pool the olbd >>can be used to keep track of the status of a file, if it is open for >>reading, in which case it cannot be opened by another process for writing >>or if a file is open for writing in which case it cannot be opened by >>anybody else. > > That's also the semantic in xrootd. When a file is open for reading, any > available node can host the file. If the file is open for writing, only > one r/w node is allowed to host the file. I will tighten these rules to > make sure that a file will not be replicated if it is being hosted by > a r/w node. > > I think the problem in xrdcp stemmed from a misunderstanding of what the > "force" option really does. That option exists in both rootd and xrootd > and both have exactly the same semantics (I tried very hard to > duplicate the semantics of rootd in this area). The force option was mainly introduced to clear the file in-use lock that might have been left over from a rootd server (software/hardware) crash (when the code was less stable and to avoid sys admin interference to clean up the situation). Basically it was a kind of back door that was not supposed to be used unless very needed. Cheers, Fons. -- Org: CERN, European Laboratory for Particle Physics. Mail: 1211 Geneve 23, Switzerland E-Mail: [log in to unmask] Phone: +41 22 7679248 WWW: http://www.rademakers.org/fons/ Fax: +41 22 7679480