Switching Storage Engines¶

As of version 3.2, Percona Server for MongoDB runs with WiredTiger by default. You can select a storage engine using the --storageEngine command-line option when you start mongod. Alternatively, you can set the storage.engine option in the configuration file (by default, /etc/mongod.conf).

Data created by one storage engine is not compatible with other storage engines, because each one has its own data model. When changing the storage engine, you have to do one of the following:

• If you simply want to temporarily test a storage engine, change to a different data directory with the --dbpath command-line option:

  $ service mongod stop
  $ mongod --storageEngine PerconaFT --dbpath <dataDirForPerconaFT>
  

  Note

  Make sure that the user running mongod has read and write permissons for the new data directory.

• If you want to permanently switch to a different storage engine and do not have any valuable data in your database, clean out the default data directory and edit the configuration file:

  $ service mongod stop
  $ rm -rf /var/lib/mongodb/*
  $ sed -i '/engine: \*PerconaFT/s/#//g' /etc/mongod.conf
  $ service mongod start
  

• If there is data that you want to migrate and make compatible with the new storage engine, use the mongodump and mongorestore utilities:

  $ mongodump --out <dumpDir>
  $ service mongod stop
  $ rm -rf /var/lib/mongodb/*
  $ sed -i '/engine: \*PerconaFT/s/#//g' /etc/mongod.conf
  $ service mongod start
  $ mongorestore <dumpDir>
  

Configuring PerconaFT¶

You can configure the PerconaFT storage engine using either command-line options or corresponding parameters in the /etc/mongod.conf file. The configuration file is formatted in YAML. For example:

storage:
  engine: PerconaFT
  PerconaFT:
    engineOptions:
      cacheSize: 53687091200
      journalCommitInterval: 100
    collectionOptions:
      compression: zlib
    indexOptions:
      compression: zlib

Setting parameters in the previous example configuration file is the same as starting the mongod daemon with the following options:

$ mongod --storageEngine PerconaFT \
  --PerconaFTEngineCacheSize 53687091200 \
  --PerconaFTEngineJournalCommitInterval 100 \
  --PerconaFTCollectionCompression zlib \
  --PerconaFTIndexCompression zlib

The following options are available (with corresponding YAML configuration file parameters):

option --PerconaFTCollectionCompression¶

Config:	storage.PerconaFT.collectionOptions.compression
Default:	zlib
Values:	none, zlib, lzma, quicklz

Specifies the PerconaFT collection compression method.

option --PerconaFTCollectionFanout¶

Config:	storage.PerconaFT.collectionOptions.fanout
Default:	16

Specifies the PerconaFT collection fanout.

option --PerconaFTCollectionPageSize¶

Config:	storage.PerconaFT.collectionOptions.pageSize
Default:	4194304 (4 MiB)

Specifies the PerconaFT collection page size in bytes.

option --PerconaFTCollectionReadPageSize¶

Config:	storage.PerconaFT.collectionOptions.readPageSize
Default:	65536 (64 KiB)

Specifies the PerconaFT collection read page size in bytes.

option --PerconaFTEngineCacheSize¶

Config:	storage.PerconaFT.engineOptions.cacheSize
Default:	0

Specifies the PerconaFT storage engine cache size in bytes.

option --PerconaFTEngineCleanerIterations¶

Config:	storage.PerconaFT.engineOptions.cleanerIterations
Default:	5

Specifies the number of PerconaFT storage engine cleaner iterations.

option --PerconaFTEngineCleanerPeriod¶

Config:	storage.PerconaFT.engineOptions.cleanerPeriod
Default:	2

Specifies the PerconaFT storage engine cleaner period in seconds.

option --PerconaFTEngineCompressBuffersBeforeEviction¶

Config:	storage.PerconaFT.engineOptions.compressBuffersBeforeEviction
Default:	false

Specifies whether the PerconaFT storage engine should compress buffers before eviction.

option --PerconaFTEngineDirectio¶

Config:	storage.PerconaFT.engineOptions.directio
Default:	false

Specifies whether the PerconaFT storage engine should use Direct I/O.

option --PerconaFTEngineFsRedzone¶

Config:	storage.PerconaFT.engineOptions.fsRedzone
Default:	5

Specifies the PerconaFT storage engine filesystem redzone.

option --PerconaFTEngineJournalCommitInterval¶

Config:	storage.PerconaFT.engineOptions.journalCommitInterval
Default:	100

Specifies the PerconaFT storage engine journal commit interval in milliseconds.

option --PerconaFTEngineLockTimeout¶

Config:	storage.PerconaFT.engineOptions.lockTimeout
Default:	100

Specifies the PerconaFT storage engine lock wait timeout in milliseconds.

option --PerconaFTEngineLocktreeMaxMemory¶

Config:	storage.PerconaFT.engineOptions.locktreeMaxMemory
Default:	0

Specifies the PerconaFT storage engine locktree size in bytes.

option --PerconaFTEngineLogDir¶

Config:	storage.PerconaFT.engineOptions.logDir
Default:

Specifies the directory for the PerconaFT storage engine transaction log.

option --PerconaFTEngineNumCachetableBucketMutexes¶

Config:	storage.PerconaFT.engineOptions.numCachetableBucketMutexes
Default:	1048576

Specifies the number of PerconaFT storage engine num cachetable bucket mutexes.

option --PerconaFTIndexCompression¶

Config:	storage.PerconaFT.indexOptions.compression
Default:	zlib
Values:	none, zlib, lzma, quicklz

Specifies the PerconaFT index compression method.

option ---PerconaFTIndexFanout¶

Config:	storage.PerconaFT.indexOptions.fanout
Default:	16

Specifies the PerconaFT index fanout.

option --PerconaFTIndexPageSize¶

Config:	storage.PerconaFT.indexOptions.pageSize
Default:	4194304 (4 MiB)

Specifies the PerconaFT index page size in bytes.

option --PerconaFTIndexReadPageSize¶

Config:	storage.PerconaFT.indexOptions.readPageSize
Default:	65536 (64 KiB)

Specifies the PerconaFT index read page size in bytes.