diff options
Diffstat (limited to 'src/ceph/doc/dev/mds_internals/data-structures.rst')
| -rw-r--r-- | src/ceph/doc/dev/mds_internals/data-structures.rst | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/src/ceph/doc/dev/mds_internals/data-structures.rst b/src/ceph/doc/dev/mds_internals/data-structures.rst new file mode 100644 index 0000000..1197b62 --- /dev/null +++ b/src/ceph/doc/dev/mds_internals/data-structures.rst @@ -0,0 +1,36 @@ +MDS internal data structures +============================== + +*CInode* + CInode contains the metadata of a file, there is one CInode for each file. + The CInode stores information like who owns the file, how big the file is. + +*CDentry* + CDentry is the glue that holds inodes and files together by relating inode to + file/directory names. A CDentry links to at most one CInode (it may not link + to any CInode). A CInode may be linked by multiple CDentries. + +*CDir* + CDir only exists for directory inode, it's used to link CDentries under the + directory. A CInode can have multiple CDir when the directory is fragmented. + +These data structures are linked together as:: + + CInode + CDir + | \ + | \ + | \ + CDentry CDentry + CInode CInode + CDir CDir + | | \ + | | \ + | | \ + CDentry CDentry CDentry + CInode CInode CInode + +As this doc is being written, size of CInode is about 1400 bytes, size of CDentry +is about 400 bytes, size of CDir is about 700 bytes. These data structures are +quite large. Please be careful if you want to add new fields to them. + |