website/content/docs/3.0/tasks/configure/rocksdb.md

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RocksDB Config	Learn how to configure namespace in TiKV.	3.0 parent weight Configure 6

TiKV uses RocksDB as its underlying storage engine for storing both Raft logs and KV (key-value) pairs.

{{< info >}} RocksDB was chosen for TiKV because it provides a highly customizable persistent key-value store that can be tuned to run in a variety of production environments, including pure memory, Flash, hard disks, or HDFS, it supports various compression algorithms, and it provides solid tools for production support and debugging. {{< /info >}}

TiKV creates two RocksDB instances on each Node:

• A rocksdb instance that stores most TiKV data
• A raftdb that stores Raft logs and has a single column family called raftdb.defaultcf

The rocksdb instance has three column families:

Column family	Purpose
rocksdb.defaultcf	Stores actual KV pairs for TiKV
rocksdb.writecf	Stores commit information in the MVCC model

RocksDB can be configured on a per-column-family basis. Here's an example:

[rocksdb]
max-background-jobs = 8

RocksDB configuration options

max-background-jobs

• The number of background threads in RocksDB
• Default value: 8
• Minimum value: 1

max-sub-compactions

• The number of sub-compaction operations performed concurrently in RocksDB
• Default value: 3
• Minimum value: 1

max-open-files

• The total number of files that RocksDB can open
• Default value: 40960
• Minimum value: -1

max-manifest-file-size

• The maximum size of a RocksDB Manifest file
• Default value: 128MB
• Minimum value: 0
• Unit: B|KB|MB|GB

create-if-missing

• Determines whether to automatically create a DB switch
• Default value: true

wal-recovery-mode

• WAL recovery mode
• Optional values: 0 (TolerateCorruptedTailRecords), 1 (AbsoluteConsistency), 2 (PointInTimeRecovery), 3 (SkipAnyCorruptedRecords)
• Default value: 2
• Minimum value: 0
• Maximum value: 3

wal-dir

• The directory in which WAL files are stored
• Default value: /tmp/tikv/store

wal-ttl-seconds

• The living time of the archived WAL files. When the value is exceeded, the system deletes these files.
• Default value: 0
• Minimum value: 0
• unit: second

wal-size-limit

• The size limit of the archived WAL files. When the value is exceeded, the system deletes these files.
• Default value: 0
• Minimum value: 0
• Unit: B|KB|MB|GB

enable-statistics

• Determines whether to automatically optimize the configuration of Rate LImiter
• Default value: false

stats-dump-period

• Enables or disables Pipelined Write
• Default value: true

compaction-readahead-size

• The size of readahead when compaction is being performed
• Default value: 0
• Minimum value: 0
• Unit: B|KB|MB|GB

writable-file-max-buffer-size

• The maximum buffer size used in WritableFileWrite
• Default value: 1MB
• Minimum value: 0
• Unit: B|KB|MB|GB

use-direct-io-for-flush-and-compaction

• Determines whether to use O_DIRECT for both reads and writes in background flush and compactions
• Default value: false

rate-bytes-per-sec

• The maximum rate permitted by Rate Limiter
• Default value: 0
• Minimum value: 0
• Unit: Bytes

rate-limiter-mode

• Rate LImiter mode
• Optional values: 1 (ReadOnly), 2 (WriteOnly), 3 (AllIo)
• Default value: 2
• Minimum value: 1
• Maximum value: 3

auto-tuned

• Determines whether to automatically optimize the configuration of the Rate LImiter
• Default value: false

enable-pipelined-write

• Enables or disables Pipelined Write
• Default value: true

bytes-per-sync

• The rate at which OS incrementally synchronizes files to disk while these files are being written asynchronously
• Default value: 1MB
• Minimum value: 0
• Unit: B|KB|MB|GB

wal-bytes-per-sync

• The rate at which OS incrementally synchronizes WAL files to disk while the WAL files are being written
• Default value: 512KB
• Minimum value: 0
• Unit: B|KB|MB|GB

info-log-max-size

• The maximum size of Info log
• Default value: 1GB
• Minimum value: 0
• Unit: B|KB|MB|GB

info-log-roll-time

• The time interval at which Info logs are truncated. If the value is 0s, logs are not truncated.
• Default value: 0s

info-log-keep-log-file-num

• The maximum number of kept log files
• Default value: 10
• Minimum value: 0

info-log-dir

• The directory in which logs are stored
• Default value: ""