[Lustre-devel] Doubly indexed tree / changelogs

[Alex Zhuravlev]

IMHO, it'd be useful to insert aggregations into that index.
just to keep the index small. say, subtree?

thanks, Alex

Peter Braam wrote:
> 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.
> 
> Peter
> 
> 
> 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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> 
>