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From Jonathan Ellis <>
Subject Re: real leveldb vs cassandra leveldb
Date Wed, 13 Feb 2013 15:32:35 GMT
The only point here that would make a difference in practice is
leveldb using a worse hash function.  For us it's not worth making
partitioning worse to make compaction better.

On Mon, Feb 11, 2013 at 12:53 PM, Radim Kolar <> wrote:
> real leveldb is better in lot of areas:
> L0 are 1/10 of L1 sstable size
> tables can be promoted to upper levels if no merging is needed (there is
> hole)
> variable number of sstables per level, but it tries to keep 1:10:100 sstable
> ratios. Not hard requirement
> very important - better hash function. murmur and md5 hashes are unsuitable
> for ldb because it turns key sequence into more or less random noise.
> Changing hash function to leveldb one gives about 8 times speed increase
> during seq. writes because far less table merges is needed
> better merge policy: merge 1 table + up to 10 tables from next level into
> next + 2 level.

Jonathan Ellis
Project Chair, Apache Cassandra

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