Bazaar, OLPC, and the "no-packs" repository format.

Aaron Bentley aaron.bentley at utoronto.ca
Wed Dec 19 19:07:10 GMT 2007


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Hi all,

I was talking with Mike Fletcher of the OLPC project yesterday, and he
was saying there's a good chance that OLPC will promote Bazaar.

The OLPC laptop is a unique device, and two differences are especially
important when considering Bazaar:

1. Its primary storage is flash memory, so its developers are write-phobic.
2. Instead of a conventional filesystem, it has a special file API that
is backed by an SQLite database

1 is a definite negative for Bazaar, since our new pack format does
rewrites quite frequently.  But 2 works in our favour, for reasons I'll
explain.

Another thing that works in our favour is our habit of supporting
multiple repository formats.  It's quite feasible to create a plugin
that supplies a new repository format designed specially for OLPC.

If we were to create an OLPC repository format, many of the restrictions
in our current designs would not apply.  We design for SFTP/FTP usage,
but that would not be needed here.  Similarly, we design for common
filesystems, where it is not efficient to have lots of little files.

But because of 2, the OLPC environment should be highly forgiving of a
repository design with lots of little files.  So an OLPC design could be
"no-packs"; basically the same data as we store in our current packs,
put directly into the file store.

Such a design could be very efficient on OLPC, and because its storage
is flash-based, data retrieval is very, very fast.

Aaron
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