domains_config
This section contains the configuration of the YDB cluster root domain, including the Blob Storage (binary object storage) and State Storage configurations.
Note
Not required for clusters with automatic configuration of State Storage and static groups.
Syntax
domains_config:
domain:
- name: <root domain name>
storage_pool_types: <Blob Storage configuration>
state_storage: <State Storage configuration>
security_config: <authentication configuration>
Note
Formally, the domain field can contain many elements as it is a list. However, only the first element is meaningful; the rest will be ignored (there can only be one "domain" in a cluster).
Blob Storage Configuration
Note
Not required for clusters with automatic configuration of State Storage and static groups.
This section defines one or more types of storage pools available in the cluster for database data with the following configuration options:
- Storage pool name
- Device properties (for example, disk type)
- Data encryption (on/off)
- Fault tolerance mode
The following fault tolerance modes are available:
| Mode | Description |
|---|---|
none |
There is no redundancy. Applies for testing. |
block-4-2 |
Redundancy factor of 1.5, applies to single data center clusters. |
mirror-3-dc |
Redundancy factor of 3, applies to multi-data center clusters. |
Syntax
storage_pool_types:
- kind: <storage pool name>
pool_config:
box_id: 1
encryption_mode: <optional, specify 1 to encrypt data on the disk>
erasure_species: <fault tolerance mode name - none, block-4-2, or mirror-3-dc>
kind: <storage pool name - specify the same value as above>
pdisk_filter:
- property:
- type: <device type to be compared with the one specified in host_configs.drive.type>
vdisk_kind: Default
- kind: <storage pool name>
...
Each database in the cluster is assigned at least one of the available storage pools selected in the database creation operation. The names of storage pools among those assigned can be used in the DATA attribute when defining column groups in YQL operators CREATE TABLE/ALTER TABLE.
State Storage Configuration
Note
Not required for clusters with automatic configuration of State Storage and static groups.
State Storage is an independent in-memory storage for variable data that supports internal YDB processes. It stores data replicas on multiple assigned nodes.
State Storage usually does not need scaling for better performance, so the number of nodes in it must be kept as small as possible taking into account the required level of fault tolerance.
State Storage availability is key for a YDB cluster because it affects all databases, regardless of which storage pools they use. To ensure fault tolerance of State Storage, its nodes must be selected to guarantee a working majority in case of expected failures.
The following guidelines can be used to select State Storage nodes:
| Cluster type | Min number of nodes |
Selection guidelines |
|---|---|---|
| Without fault tolerance | 1 | Select one random node. |
| Within a single availability zone | 5 | Select five nodes in different block-4-2 storage pool failure domains to ensure that a majority of 3 working nodes (out of 5) remain when two domains fail. |
| Geo-distributed | 9 | Select three nodes in different failure domains within each of the three mirror-3-dc storage pool availability zones to ensure that a majority of 5 working nodes (out of 9) remain when the availability zone + failure domain fail. |
When deploying State Storage on clusters that use multiple storage pools with a possible combination of fault tolerance modes, consider increasing the number of nodes and spreading them across different storage pools because unavailability of State Storage results in unavailability of the entire cluster.
Syntax
state_storage:
- ring:
node: <StateStorage node array>
nto_select: <number of data replicas in StateStorage>
ssid: 1
Each State Storage client (for example, DataShard tablet) uses nto_select nodes to write copies of its data to State Storage. If State Storage consists of more than nto_select nodes, different nodes can be used for different clients, so you must ensure that any subset of nto_select nodes within State Storage meets the fault tolerance criteria.
Odd numbers must be used for nto_select because using even numbers does not improve fault tolerance in comparison to the nearest smaller odd number.
Complete Configuration Examples
Single Data Center with block-4-2 Erasure
domains_config:
domain:
- name: Root
storage_pool_types:
- kind: ssd
pool_config:
box_id: 1
erasure_species: block-4-2
kind: ssd
pdisk_filter:
- property:
- type: SSD
vdisk_kind: Default
state_storage:
- ring:
node: [1, 2, 3, 4, 5, 6, 7, 8]
nto_select: 5
ssid: 1
Multi Data Center with mirror-3-dc Erasure
domains_config:
domain:
- name: global
storage_pool_types:
- kind: ssd
pool_config:
box_id: 1
erasure_species: mirror-3-dc
kind: ssd
pdisk_filter:
- property:
- type: SSD
vdisk_kind: Default
state_storage:
- ring:
node: [1, 2, 3, 4, 5, 6, 7, 8, 9]
nto_select: 9
ssid: 1
No Fault Tolerance (none) - For Testing
domains_config:
domain:
- name: Root
storage_pool_types:
- kind: ssd
pool_config:
box_id: 1
erasure_species: none
kind: ssd
pdisk_filter:
- property:
- type: SSD
vdisk_kind: Default
state_storage:
- ring:
node: [1]
nto_select: 1
ssid: 1
Multiple Storage Pool Types
domains_config:
domain:
- name: Root
storage_pool_types:
- kind: ssd
pool_config:
box_id: '1'
erasure_species: block-4-2
kind: ssd
pdisk_filter:
- property:
- {type: SSD}
vdisk_kind: Default
- kind: rot
pool_config:
box_id: '1'
erasure_species: block-4-2
kind: rot
pdisk_filter:
- property:
- {type: ROT}
vdisk_kind: Default
- kind: rotencrypted
pool_config:
box_id: '1'
encryption_mode: 1
erasure_species: block-4-2
kind: rotencrypted
pdisk_filter:
- property:
- {type: ROT}
vdisk_kind: Default
- kind: ssdencrypted
pool_config:
box_id: '1'
encryption_mode: 1
erasure_species: block-4-2
kind: ssdencrypted
pdisk_filter:
- property:
- {type: SSD}
vdisk_kind: Default
state_storage:
- ring:
node: [1, 16, 31, 46, 61, 76, 91, 106]
nto_select: 5
ssid: 1