[Lustre-devel] Doubly indexed tree / changelogs

Peter Braam Peter.Braam at Sun.COM
Sun Sep 21 23:58:56 PDT 2008

Objects can be in many filesets, and be added to some, removed from others.

I think this is an almost arbitrary collection of pairs (FID, fileset-id)
and we need it indexed by both.


On 9/22/08 1:52 PM, "Alex Zhuravlev" <Alex.Zhuravlev at Sun.COM> wrote:

> can object migrate between filesets? if not, we probably
> can use fid's sequence as a record in that index?
> thanks, Alex
> Peter Braam wrote:
>> 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?
>> Peter
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