Hi Yan Zheng
Now my questions: 1) I performed all of this testing to understand what would be the minimum size (reported by df) of a file of 1 char and I am still not able to find a clear answer. In a regular posix file system, the size of a 1 char (1 byte) file is actually constrained by the filesystem block size. A 1 char file would occupy 4 KB in a filesystem configured with a 4 KB blocksize. In ceph / cephfs I would expect that a 1 char file would be constrained by the Object size x Number of replicas. However, I was not able to understand the numbers I was getting and that was why I started to dig on this topic. Can you actually also clarify this question? rbytes is sum of sizes of file under the directory, nothing do with block size. If there are sparse files, rbytes of root directory can be larger then used space of FS,
Maybe I did not explain myself clearly. I am not saying that block size has something to do with rbytes, I was just making a comparison with what I expect in a regular POSIX filesystem. Let me put the question in the following / different way:
1) I know that, if I only have one char file in a ext4 filesystem, where my filesystem was set with a 4KB blocksize, a df would show 4KB as used space.
2) now imagine that I only have one char file in my Cephfs filesystem, and the layout of my file is object_size=512K, stripe_count=2, and stripe_unit=256K. Also assume that I have set my cluster to have 3 replicates. What would be the used space reported by a df command in this case?
My naive assumption would be that a df should show as used space 512KB x 3. Is this correct?
Cheers Goncalo -- Goncalo Borges Research Computing ARC Centre of Excellence for Particle Physics at the Terascale School of Physics A28 | University of Sydney, NSW 2006 T: +61 2 93511937 _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
