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Hi Andy, Is there a way to to enforce a read-only rule for particular data servers? If this is possible, I can ensure that newly written data avoids the systems that need to be "LVM'ed", while allowing the existing data to be read. I am curious if I can replicate data under this scenario using xrdcp, or will I still have to take the read-only systems off-line to move the data? I am concerned about the granularity of recovery actions in our systems under LVM, but I need to support larger pathnames now. The pathnames are being driven by the physics users and the use of metadata in the path components. Patrick Andrew Hanushevsky wrote: > Hi Patrick, > > You are quite right that the design of the cache does impose limits on > file names. The oss was designed almost 10 years ago when there were no > integrated LVM's and few that worked really well and users kept path > names to less that 200 characters. Over the years, as LVM's became > common, the oss turned into the "poor man's LVM". In general, we don't > recommend using it if you have ready access to a suitable LVM. While, > yes, you do give up some features (like fine-grained recoverability and > application-directed partition selection) the other > limitations may be even more annoying. We'll make sure that this > restriction is prominently mentioned in the manual. > > The path you've chosen is about the only one that will work (i.e., > copying off the data and creating a single filesystem using an LVM). > > Now, we do have some ideas on how to remove the pathname length > restriction but wonder if it's really worth the trouble of doing it, > given that LVM's provide practically the same basic features. Any thoughts? > > Andy > > P.S. What's the driving force for very long path names at your site? > > > On Sat, 1 Mar 2008, Patrick McGuigan wrote: > >> Hi, >> >> Some of our data servers have two disks and I am using the oss.cache >> directive to use both disks to support a single namespace. However, >> it looks like the users of our applications have already run into a >> problem. All of the files are stored in one directory (for a single >> cache) and the filename is the full namespace path with "/" >> substituted with "%". Our problem arises from the fact that full >> namespace path is now limited to the leafname length of the filesystem >> (255 characters) when writing to the cache directory. >> >> I see a couple of ways to mediate the problem; removing one disk or >> using and LVM to create one drive in the OS. I am curious if there >> are other alternatives? >> >> If I have to move to one disk, I would like to migrate the data in the >> existing caches to other data servers while I rework the existing >> system. What is the best way to migrate this data? I am planning on >> taking the "problem" data server off-line and use xrdcp to move the >> data to the other servers. >> >> Regards, >> >> Patrick >>