**Use case**

Currently, `system.replicas` table has `total_replicas` and `active_replicas` columns which are useful to check/alert when some replicas are down. One problem, these columns are numbers. They tell when there is a problem, but you need to further check ZooKeeper or query all the nodes to detect what exact replicas (hosts) are down/inactive/have problems.

**Describe the solution you'd like**

Add a replicas column maybe as a map which would contain the replica name, and it's status. Or, add 2 array columns with `replica_names` and `active_replica_names`

**Alternative**

Something along the line

```sql
select path, value from system.zookeeper where path IN (
    select concat(path, '/', name) from system.zookeeper where path in (select concat(zookeeper_path, '/replicas') from system.replicas)
)
and name = 'is_active'
```
break;
        }
        catch (const zkutil::KeeperException & e)
        {
            if (e.code == Coordination::Error::ZNONODE)
                continue;
            throw;
        }
    }
}
bool StorageReplicatedMergeTree::unlockSharedData(const IMergeTreeDataPart & part) const
{
    if (!part.volume)
        return true;
    DiskPtr disk = part.volume->getDisk();
    if (!disk || !disk->supportZeroCopyReplication())
        return true;
    String zero_copy = fmt::format("zero_copy_{}", DiskType::toString(disk->getType()));
    zkutil::ZooKeeperPtr zookeeper = tryGetZooKeeper();
    if (!zookeeper)
        return true;
    String id = part.getUniqueId();
    boost::replace_all(id, "/", "_");
    String zookeeper_part_node = fs::path(zookeeper_path) / zero_copy / "shared" / part.name;
    String zookeeper_part_uniq_node = fs::path(zookeeper_part_node) / id;
    String zookeeper_node = fs::path(zookeeper_part_uniq_node) / replica_name;
    LOG_TRACE(log, "Remove zookeeper lock {}", zookeeper_node);
    zookeeper->tryRemove(zookeeper_node);
    Strings children;
    zookeeper->tryGetChildren(zookeeper_part_uniq_node, children);