jm + bdb   6

RocksDB
' A persistent key-value store for fast storage environments', ie. BerkeleyDB/LevelDB competitor, from Facebook.
RocksDB builds on LevelDB to be scalable to run on servers with many CPU cores, to efficiently use fast storage, to support IO-bound, in-memory and write-once workloads, and to be flexible to allow for innovation.

We benchmarked LevelDB and found that it was unsuitable for our server workloads. Thebenchmark results look awesome at first sight, but we quickly realized that those results were for a database whose size was smaller than the size of RAM on the test machine - where the entire database could fit in the OS page cache. When we performed the same benchmarks on a database that was at least 5 times larger than main memory, the performance results were dismal.

By contrast, we've published the RocksDB benchmark results for server side workloads on Flash. We also measured the performance of LevelDB on these server-workload benchmarks and found that RocksDB solidly outperforms LevelDB for these IO bound workloads. We found that LevelDB's single-threaded compaction process was insufficient to drive server workloads. We saw frequent write-stalls with LevelDB that caused 99-percentile latency to be tremendously large. We found that mmap-ing a file into the OS cache introduced performance bottlenecks for reads. We could not make LevelDB consume all the IOs offered by the underlying Flash storage.


Lots of good discussion at https://news.ycombinator.com/item?id=6736900 too.
flash  ssd  rocksdb  databases  storage  nosql  facebook  bdb  disk  key-value-stores  lsm  leveldb 
november 2013 by jm
Lightning Memory-Mapped Database
Sounds like a good potential replacement for Berkeley DB, at least for cases where LevelDB isn't proving practical.
LMDB is a database storage engine similar to LevelDB or BDB which database authors often use as a base for building databases on top of. LMDB was designed as a replacement for BDB within the OpenLDAP project but it has been pretty useful to use with other databases as well. It’s API design is highly influenced by BDB so that replacing BDB is straightforward.


Licensed under the OpenLDAP Public License (is that BSDish?)
openldap  lmdb  databases  bdb  berkeley-db  storage  persistence  oss  open-source 
july 2013 by jm
Project Voldemort: measuring BDB space consumption
HOWTO measure this using the BDB-JE command line tools. this is exposed through JMX as the CleanerBacklog metric, too, I think, but good to bookmark just in case
voldemort  cleaner  bdb  ops  space  storage  monitoring  debug 
june 2013 by jm
Berkeley DB Java Edition Architecture [PDF]
background white paper on the BDB-JE innards and design, from 2006. Still pretty accurate and good info
bdb-je  java  berkeley-db  bdb  design  databases  pdf  white-papers  trees 
may 2013 by jm
Making sense out of BDB-JE fast stats
good info on the system metrics recorded by BDB-JE's EnvironmentStats code, particularly where cache and cleaner activity are concerned. Particularly useful for Voldemort
voldemort  caching  bdb  bdb-je  storage  tuning  ops  metrics  reference 
may 2013 by jm
Announcing the Voldemort 1.3 Open Source Release
new release from LinkedIn -- better p90/p99 PUT performance, improvements to the BDB-JE storage layer, massively-improved rebalance performance
voldemort  linkedin  open-source  bdb  nosql 
march 2013 by jm

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