[OpenAFS-devel] Large Caches: Implementation Discussion

[Derek Atkins]

There were a few open issues with regards to my large-cache patch that
I sent in.  As I recall, the issues were:

	1) The name of the afsd option: I had used -files_per_subdir
           but there was some objection that what I was really looking
           for was the log2 of the number of files per subdir.  Do
           people really care?  If so, do you have a suggestion?

	2) The default subdirectory size.  I default to 2^11 (2048)
           files per subdir, which seems to work well for me.  I don't
           think this was an issue, but I thought I'd mention it just
           in case.

	3) Using 'D*' as the name of subdirs.  If you don't like this,
           please suggest an alternative.  I personally don't have a
           strong opinion, but I figured 'D == Directory' was a
           reasonable choice.

	4) Compatibility with old-style caches.  As I mentioned, this
           new cache method will destroy your existing cache files and
           build a new one in subdirs.  In effect, it will clear out
           your old cache, so moving forward to a new-style cache will
           DTRT and clear your cache directory appropriately.  One
           side effect is that if you ever try to use an old
           (current?) cache-style afsd, it will complain about all the
           subdirs (because you cannot unlink() a directory).

	5) Over-riding the default "files_per_subdir" value even if
           the user supplies a bad value.  As I said, I do the same
           think that chunkSize does in terms of processing user
           input.  I don't have a strong preference how this behaves.
           I really don't expect users to even use the option.

	6) It was requested to supply an option to turn this
           functionality off.  Consensus (as the IETF uses the phrase)
           seems to be that this isn't needed.

	7) There is no issue #7.

Once we clear up this list of issues we can get this code into the
repository.  So, is there consensus on any of these issues?  If you
have issues with the large-cache patch, please speak up.

Thanks!

-derek
-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
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