# system.clusters {#system-clusters} Contains information about clusters available in the config file and the servers in them. Columns: - `cluster` ([String](../../sql-reference/data-types/string.md)) — The cluster name. - `shard_num` ([UInt32](../../sql-reference/data-types/int-uint.md)) — The shard number in the cluster, starting from 1. - `shard_weight` ([UInt32](../../sql-reference/data-types/int-uint.md)) — The relative weight of the shard when writing data. - `replica_num` ([UInt32](../../sql-reference/data-types/int-uint.md)) — The replica number in the shard, starting from 1. - `host_name` ([String](../../sql-reference/data-types/string.md)) — The host name, as specified in the config. - `host_address` ([String](../../sql-reference/data-types/string.md)) — The host IP address obtained from DNS. - `port` ([UInt16](../../sql-reference/data-types/int-uint.md)) — The port to use for connecting to the server. - `is_local` ([UInt8](../../sql-reference/data-types/int-uint.md)) — Flag that indicates whether the host is local. - `user` ([String](../../sql-reference/data-types/string.md)) — The name of the user for connecting to the server. - `default_database` ([String](../../sql-reference/data-types/string.md)) — The default database name. - `errors_count` ([UInt32](../../sql-reference/data-types/int-uint.md)) — The number of times this host failed to reach replica. - `slowdowns_count` ([UInt32](../../sql-reference/data-types/int-uint.md)) — The number of slowdowns that led to changing replica when establishing a connection with hedged requests. - `estimated_recovery_time` ([UInt32](../../sql-reference/data-types/int-uint.md)) — Seconds remaining until the replica error count is zeroed and it is considered to be back to normal. **Example** Query: ```sql SELECT * FROM system.clusters LIMIT 2 FORMAT Vertical; ``` Result: ```text Row 1: ────── cluster: test_cluster_two_shards shard_num: 1 shard_weight: 1 replica_num: 1 host_name: 127.0.0.1 host_address: 127.0.0.1 port: 9000 is_local: 1 user: default default_database: errors_count: 0 slowdowns_count: 0 estimated_recovery_time: 0 Row 2: ────── cluster: test_cluster_two_shards shard_num: 2 shard_weight: 1 replica_num: 1 host_name: 127.0.0.2 host_address: 127.0.0.2 port: 9000 is_local: 0 user: default default_database: errors_count: 0 slowdowns_count: 0 estimated_recovery_time: 0 ``` **See Also** - [Table engine Distributed](../../engines/table-engines/special/distributed.md) - [distributed_replica_error_cap setting](../../operations/settings/settings.md#settings-distributed_replica_error_cap) - [distributed_replica_error_half_life setting](../../operations/settings/settings.md#settings-distributed_replica_error_half_life) [Original article](https://clickhouse.com/docs/en/operations/system-tables/clusters)