[Lustre-devel] Doubly indexed tree / changelogs

Peter Braam Peter.Braam at Sun.COM
Sun Sep 21 16:40:25 PDT 2008

Hi Nikita, Nathan -

After some pondering I have come to two conclusions.

To encode filesets, we need a tree that makes two iterations fast:

1. list all filesets that contain a certain object
2. list all objects in a certain fileset

Is there a doubly indexed tree for this?

Secondly, to make the changelogs useful and scalable for filesets we will
need to be able to list all changelog entries associated with a certain
inode efficiently.  I see two ways to do this ­ one is an auxiliary
directory file mapping inodes to many changelog entries, the second is to
embed forward and backward pointers in the changelog entries to build a
linked list rooted at the inode (using an EA in the inode pointing to the
first and last element of the list).  Both have some overheads.  What are
your thoughts?

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