Re: New HDB backend MDB

Hi,

You say on one slide that

"
 o Surveying the landscape revealed no other database libraries with
the desired characteristic
"

But SQLite3 with WAL (write-ahead logging) has very similar
characteristics to your MDB: MVCC, serialized writing, support for
in-memory and on-disk databases (MDB doesn't do on-disk).

Did you consider SQLite3 w/ WAL?

My suspicion is that if you don't need (or want) the full overhead of
SQL then MDB can probably perform much better than SQLite3 w/ WAL.
Have you benchmarked the two?

What makes your write throughput so slow relative to BDB?  Do you
fsync() more often than you have to?  When do you fsync()?  Your write
transaction rate does seem high for, say, a single traditional disk...
 What is the on-disk file format like?  I gather the file format is
the same as memory + whatever appends are needed as pages are
allocated.  The DB format reminds me a lot of ZFS, with just two
ubberblocks (pages #0 and #1) and with btrees (well, one b-tree,
right?) instead of directories and files.

This looks very interesting.  Thanks,

Nico
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