Hello Sage, sage writes: >The ceph transport layer does a crc32c over all data that passes over the >wire to catch bit flips from the network (TCP's checksumming isn't very >strong). This isn't truly end-to-end protection, though, as bit flips on >the client after the applicate write(2) but before writeback starts, or on >the server after receiving the message won't be detected. > >Btrfs does do it's own checksumming, so in theory if we match the function >on the client we can do better. There is also some end-to-end data >integrity infrastructure in the kernel that IIRC Martin Peterson was >working on. Much that is in the block layer, though; the only parts that >would be useful to ceph would relate to the userspace interface and page >cache. I'm not sure what the current state of that work is. > >It would be nice to see end-to-end protection (complete with some sort of >userspace api) in action on a local file system (probably btrfs, which >actually stores checksums) as a model before trying to build it into a >more complicated distributed file system...
Thanks very much for this info. Good to know that Ceph currently does checking at network-transport level beyond what TCP does, and makes sense to me that a local-FS implementation of end to end protection facilities could be a next-step preceding distributed-FS implementation. Craig Dunwoody GraphStream Incorporated ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Ceph-devel mailing list Ceph-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/ceph-devel
