[Lustre-devel] storing SOM epoch in EA
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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