**Describe the bug**

Since we upgraded to 20.10.3.30, one of our clickhouse cluster takes much more time to start. (Up to 50 minutes, and before it took ~3 minutes)
The log file is filled with
>  <Debug> DiskLocal: Reserving 1.00 MiB on disk `default`, having unreserved 16.90 TiB

Additionally, the memory consumption increases, linearly, a lot (up to arround 230 G for us) and then drop back to normal values once clickhouse finished starting up. During that loading phase, a single CPU core is used at 100%.
If that memory is not available for the machine, clickhouse gets OOMed by the kernel.


**How to reproduce**
* Issue appeared after we upgraded to ClickHouse server version 20.10.3.30

* How could I find wich of our tables may be responsible for that ?


**Expected behavior**
A fast startup :)

throw Exception(ErrorCodes::CORRUPTED_DATA, "Duplication of version file {} and {}", fullPath(version_file.second, version_file.first), current_version_file_path);
            version_file = {current_version_file_path, disk};
        }
    }
    
    if (version_file.first.empty())
        version_file = {fs::path(relative_data_path) / MergeTreeData::FORMAT_VERSION_FILE_NAME, getStoragePolicy()->getAnyDisk()};
    bool version_file_exists = version_file.second->exists(version_file.first);
    
    if (!attach || !version_file_exists)
    {
        format_version = min_format_version;
        if (!version_file.second->isReadOnly())
        {
            auto buf = version_file.second->writeFile(version_file.first, DBMS_DEFAULT_BUFFER_SIZE, WriteMode::Rewrite, context_->getWriteSettings());
            writeIntText(format_version.toUnderType(), *buf);
            if (getContext()->getSettingsRef().fsync_metadata)
                buf->sync();
        }
    }
    else
    {
        auto buf = version_file.second->readFile(version_file.first);
        UInt32 read_format_version;
        readIntText(read_format_version, *buf);
        format_version = read_format_version;
        if (!buf->eof())
            throw Exception("Bad version file: " + fullPath(version_file.second, version_file.first), ErrorCodes::CORRUPTED_DATA);
    }
    if (format_version < min_format_version)