Check out bitcask TTL, expiry. -Alexander
@siculars http://siculars.posthaven.com Sent from my iRotaryPhone > On Apr 20, 2016, at 12:20, Shifeng Xiao <xiaoshifen...@gmail.com> wrote: > > Thanks for the information Alexander and Daniel, I appreciated it. > > We are using Riak2.0 and bitcask as backend, and we are writing the keys once > into bucket, keep it for a few hours, then delete it, never update the > existing data. > > >> On Wed, Apr 20, 2016 at 11:32 AM, Alexander Sicular <sicul...@gmail.com> >> wrote: >> Hello Shifeng, >> >> Riak uses Bitcask as its default data backend, it may also use leveldb >> as a backend but must be configured to do so[0][1]. Both bitcask[2] >> and leveldb[3] do not reclaim disk space immediately when a delete is >> issued. Incidentally, neither do updates. Because Riak is >> non-destructive, aka append only, aka no in-place updates, mutation >> operations like updates or deletes are actually writes. For example, a >> 10KB object that is updated four times in some short interval will >> consume 50KB space (original 10KB + 4 x 10KB updates) until >> merge/compaction occurs. A delete is actually a special zero byte >> value write indicating a key is marked for deletion, aka a tombstone. >> Bitcask will reclaim disk space via merge operations which may be >> controlled by the user. Leveldb reclaims disk space via compaction >> operations. >> >> Architects and Developers should take into account their update/delete >> ratios and consider how those will affect disk space consumption and >> consider how deletes operate in distributed systems in general and >> Riak in specific from an application perspective. John Daily wrote a >> must read four part series on Riak's configurable behaviors that all >> Riak developers should be familiar with. Part 3 deals specifically >> with delete related considerations[4]. >> >> Thank you, >> Alexander >> >> [0] >> http://docs.basho.com/riak/kv/latest/setup/planning/backend/leveldb/#installing-eleveldb >> [1] http://docs.basho.com/riak/kv/latest/configuring/backend/ >> [2] http://docs.basho.com/riak/kv/latest/setup/planning/backend/bitcask/ >> [3] http://docs.basho.com/riak/kv/latest/setup/planning/backend/leveldb/ >> [4] http://basho.com/posts/technical/riaks-config-behaviors-part-3/ >> >> On Wed, Apr 20, 2016 at 8:17 AM, Daniel Abrahamsson >> <daniel.abrahams...@klarna.com> wrote: >> > Hi, >> > >> > What riak version and what riak backend are you using? For leveldb you have >> > to take compaction into account, and for older bitcask versions there are >> > known issues with data not being properly deleted. >> > >> > //Daniel >> > >> > _______________________________________________ >> > riak-users mailing list >> > riak-users@lists.basho.com >> > http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com >> > >
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