[Config] Document 'snapshot' and 'wal' configuration settings

[andreyaksenov]

Product: Tarantool
Since: 3.0
Root document:

• A new Persistence topic in the Configuration section.
• New snapshot and wal sections in the Configuration reference.
• Check and update links to config options (for example, in the audit log section)

SME: @ Totktonada

Details

Important note:

tt configuration also includes WAL/snapshot storage settings (run_dir, log_dir, wal_dir, memtx_dir, vinyl_dir): https://www.tarantool.io/en/doc/latest/reference/tooling/tt_cli/configuration/.
This means that we need to understand how they work together with Tarantool settings and which approach to use to configure these settings.

Options:

• https://github.com/tarantool/tarantool/blob/f58bfc97c627f1838696697339fb3e443c05767a/src/box/lua/config/instance_config.lua#L1325
• https://github.com/tarantool/tarantool/blob/f58bfc97c627f1838696697339fb3e443c05767a/src/box/lua/config/instance_config.lua#L1244

Related topics:

• https://www.tarantool.io/en/doc/latest/concepts/data_model/persistence/
• https://www.tarantool.io/en/doc/latest/concepts/engines/memtx/#data-persistence
• https://www.tarantool.io/en/doc/latest/dev_guide/internals/file_formats/

Legacy options:

• https://www.tarantool.io/en/doc/latest/reference/configuration/#binary-logging-and-snapshots
• https://www.tarantool.io/en/doc/latest/reference/configuration/#checkpoint-daemon

| TT_SNAPSHOT_BY_INTERVAL                               | number         | 3600                                          | Community Edition  |
| TT_SNAPSHOT_BY_WAL_SIZE                               | integer        | 1e+18                                         | Community Edition  |
| TT_SNAPSHOT_COUNT                                     | integer        | 2                                             | Community Edition  |
| TT_SNAPSHOT_DIR                                       | string         | var/lib/{{ instance_name }}                   | Community Edition  |
| TT_SNAPSHOT_SNAP_IO_RATE_LIMIT                        | number         | box.NULL                                      | Community Edition  |
| TT_WAL_CLEANUP_DELAY                                  | number         | 14400                                         | Community Edition  |
| TT_WAL_DIR                                            | string         | var/lib/{{ instance_name }}                   | Community Edition  |
| TT_WAL_DIR_RESCAN_DELAY                               | number         | 2                                             | Community Edition  |
| TT_WAL_EXT_NEW                                        | boolean        | nil                                           | Enterprise Edition |
| TT_WAL_EXT_OLD                                        | boolean        | nil                                           | Enterprise Edition |
| TT_WAL_EXT_SPACES                                     | map            | nil                                           | Enterprise Edition |
| TT_WAL_MAX_SIZE                                       | integer        | 268435456                                     | Community Edition  |
| TT_WAL_MODE                                           | string         | write                                         | Community Edition  |
| TT_WAL_QUEUE_MAX_SIZE                                 | integer        | 16777216                                      | Community Edition  |