**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'
```
{
    fs::directory_iterator dir_end;
    for (const std::string & path : getDataPaths())
        for (fs::directory_iterator dir_it{fs::path(path) / "detached/"}; dir_it != dir_end; ++dir_it)
            if (dir_it->path().filename().string() == part_name)
                return true;
    return false;
}
bool StorageReplicatedMergeTree::checkIfDetachedPartitionExists(const String & partition_name)
{
    fs::directory_iterator dir_end;
    for (const std::string & path : getDataPaths())
    {
        for (fs::directory_iterator dir_it{fs::path(path) / "detached/"}; dir_it != dir_end; ++dir_it)
        {
            MergeTreePartInfo part_info;
            if (MergeTreePartInfo::tryParsePartName(dir_it->path().filename(), &part_info, format_version) && part_info.partition_id == partition_name)
                return true;
        }
    }
    return false;
}
bool StorageReplicatedMergeTree::createEmptyPartInsteadOfLost(zkutil::ZooKeeperPtr zookeeper, const String & lost_part_name)
{
    LOG_INFO(log, "Going to replace lost part {} with empty part", lost_part_name);
    auto metadata_snapshot = getInMemoryMetadataPtr();
    auto settings = getSettings();
    constexpr static auto TMP_PREFIX = "tmp_empty_";
    auto new_part_info = MergeTreePartInfo::fromPartName(lost_part_name, format_version);
    auto block = metadata_snapshot->getSampleBlock();