Hi, Jonathan. On Mon, Jul 4, 2011 at 9:42 AM, Jonathan Langevin <[email protected]> wrote:
> I've seen users show concern of Bitcask's space usage overhead. How does that > compare against LevelDB? Bitcask doesn't have much in the way of disk space "overhead" unless you mean that the space used by deleted or overwritten values is not reclaimed until after a merge. In that way LevelDB is similar since space used by deleted and overwritten items is reclaimed as they are moved into older "levels" of the DB. The behavior here is not identical, but similar in concept. By way of comparison, InnoDB imposes about a 2x space overhead cost on many common datasets but the overhead is usually fairly static. > If using a Level backend, what advantages do we lose of Bitcask? ls > replication & > availability an issue at all? The functionality provided by Riak above the storage engines (such as replication and system-wide availability) are generally not impacted by your choice of storage engine. There are two main things you would lose today: 1 - latency 2 - stability The first of these is fundamental: for many usage patterns Bitcask will have a latency advantage over LevelDB due to being able to guarantee that it will never perform more than a single disk seek per operation. The second is just about the relative immaturity of LevelDB: we have not yet seen LevelDB in production environments for an extended amount of time as we have with Bitcask. Anyone using it now as a Bitcask replacement should realize that they are on the leading edge and taking the usual risks that come with adopting new software. That said, we expect LevelDB to do well over time as one of the alternative Riak storage engines. The main reason to use LevelDB under Riak would be if your number of keys is huge and thus the RAM consumption of Bitcask would make it unsuitable. That is, we expect people to use LevelDB in the same situations that they might previously have chosen Innostore as their storage engine. -Justin _______________________________________________ riak-users mailing list [email protected] http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
