[Lustre-devel] storing SOM epoch in EA

Nikita Danilov Nikita.Danilov at Sun.COM
Wed Feb 20 08:10:08 PST 2008

Alex Zhuravlev writes:
 > Nikita Danilov wrote:
 > > One possible point here is that OSD has to do fid->ino translation
 > > anyway, and it makes sense to use the same index to store other
 > > information besides inode number. That is, we can use "object index" iam
 > > file to map fid into (ino, gen, ioepoch, LOV, ...) records, and this
 > > would not cause any additional seeks. The downside here is that object
 > > index is so heavily used, that making its records larger is going to
 > > increase the amount of IO significantly, so it only worth to place there
 > > things that we are absolutely sure will be needed for every inode.
 > well, we also need to update ioepoch when we update size/blocks.

Indeed. We still can do this for read-only and read-mostly attributes,
like LOV and avoid dirtying extra blocks in the common case.

 > thanks, Alex


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