Ordinary database engine is deprecated but there is no simple mean to change database engine to Atomic for existing databases.

Possible options:
- ALTER DATABASE MODIFY ENGINE query.
- Flag that triggers migration at ClickHouse startup.

The latter should be easier to implement. 

{
    return total_bytes;
}
void StorageStripeLog::backupData(BackupEntriesCollector & backup_entries_collector, const String & data_path_in_backup, const std::optional<ASTs> & )
{
    auto lock_timeout = getLockTimeout(backup_entries_collector.getContext());
    loadIndices(lock_timeout);
    ReadLock lock{rwlock, lock_timeout};
    if (!lock)
        throw Exception("Lock timeout exceeded", ErrorCodes::TIMEOUT_EXCEEDED);
    if (!file_checker.getFileSize(data_file_path))
        return;
    fs::path data_path_in_backup_fs = data_path_in_backup;
    auto temp_dir_owner = std::make_shared<TemporaryFileOnDisk>(disk, "tmp/");
    fs::path temp_dir = temp_dir_owner->getPath();
    disk->createDirectories(temp_dir);
    
    {
        
        String data_file_name = fileName(data_file_path);
        String hardlink_file_path = temp_dir / data_file_name;
        disk->createHardLink(data_file_path, hardlink_file_path);
        backup_entries_collector.addBackupEntry(
            data_path_in_backup_fs / data_file_name,