**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'
```
throw Exception("Part " + part->name + " fetched on wrong disk " + part->volume->getDisk()->getName(), ErrorCodes::LOGICAL_ERROR);
        replaced_disk->removeFileIfExists(replaced_part_path);
        replaced_disk->moveDirectory(part->getFullRelativePath(), replaced_part_path);
    }
    catch (const Exception & e)
    {
        
        
        if (e.code() == ErrorCodes::DIRECTORY_ALREADY_EXISTS)
            return false;
        throw;
    }
    catch (...)
    {
        write_part_log(ExecutionStatus::fromCurrentException());
        throw;
    }
    ProfileEvents::increment(ProfileEvents::ReplicatedPartFetches);
    LOG_DEBUG(log, "Fetched part {} from {}", part_name, source_replica_path);
    return true;
}
void StorageReplicatedMergeTree::startup()
{
    if (is_readonly)
        return;
    try
    {
        queue.initialize(getDataParts());
        InterserverIOEndpointPtr data_parts_exchange_ptr = std::make_shared<DataPartsExchange::Service>(*this);
        [[maybe_unused]] auto prev_ptr = std::atomic_exchange(&data_parts_exchange_endpoint, data_parts_exchange_ptr);