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Re: Issues arising from creating powerdns backend based on LMDB
Mark Zealey wrote:
4) Creating database with non-sequential keys is very bad (on 4gb
databases, 2* slower than kyoto - about 1h30 and uses more memory).
This was actually a typo - kyoto only takes about 20 minutes to generate
it so 4* slower. However, using a commit every 1m inserts (and because
Try again with commit every 100K inserts.
of a limitation in the perl module also have to close the DB/env and
reopen it) and backing it to a memdisk (which we also have to do with
kyoto), it takes about 10% less time than kyoto. Doing it against normal
disk is still very slow though. Size for a 4gb database was about 10%
more than kyoto, for kyoto outputting a 1.5gb database lmdb did 2.5gb
though. Doesn't matter too much for our purposes however.
Look at mdb_stat -ef on the resulting DB, you'll see that a large amount of
pages claimed on disk are actually free pages in the DB. Larger commits leave
more old pages behind than smaller commits.
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/