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Hi, Andy! > The real problem here is that the person is using a backdoor to modify > the file. Had the user modified the file on the disk cache and let it > migrate back down, there would not be a problem. Using backdoors opens > a whole range of problems, only one of which the user experienced. It should not be called a back door, it's a perfectly valid situation of separation production from analysis. We do this all the time at SLAC. The only difference is that we have read-only files, and this simplifies our life a lot. Whether D0 user can do it our way really depends on how they do their production. But I think that such function Jean-Yves described should exists and be configurable for those who find it necessary. Artem. > > I'm not opposed to putting in an option to do the check but I think > serious consideration needs to be given whether this is *really* the > mode of operation you want or will be happy with. > > Andy > > On Wed, 2 Mar 2005, Jean-Yves Nief wrote: > > > hello all, > > > > one of the D0 user accessing files via xrootd encountered the > > following issue: after having accessed a file via xrootd (so after being > > staged from the "master" copy stored in HPSS), he modified the master > > copy in HPSS and wanted to access the modified file via xrootd: but as > > the old version of the file was already on the disk cache, no staging > > occured of course (but that is the expected behavior obviously) and he > > grabbed the old one version, which is not what he wanted. Well as an > > emergency solution and as it was the first time it happened, I've > > deleted the old version on the disk cache so he could proceed. > > However, I think it would be nice to have some control on the validity > > of the cache: one solution would be to add the following test: in case > > the file is already in the cache, compare the creation time on the cache > > disk (t1) with the last modified time of the file stored in HPSS (t2): > > if t1<t2 then restage the file. > > it will be a very small overhead to the mechanism, each time a file is > > accessed: it have just to issue a "statx" request to the MSS. > > or maybe there is a more simple solution. > > cheers, > > JY > > > > >