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. 

try
    {
        const char * filename = "/sys/kernel/mm/transparent_hugepage/enabled";
        if (readString(filename).find("[always]") != std::string::npos)
            server.context()->addWarningMessage("Linux transparent hugepages are set to \"always\". Check " + String(filename));
    }
    catch (...)
    {
    }
    try
    {
        const char * filename = "/proc/sys/kernel/pid_max";
        if (readNumber(filename) < 30000)
            server.context()->addWarningMessage("Linux max PID is too low. Check " + String(filename));
    }
    catch (...)
    {
    }
    try
    {
        const char * filename = "/proc/sys/kernel/threads-max";
        if (readNumber(filename) < 30000)
            server.context()->addWarningMessage("Linux threads max count is too low. Check " + String(filename));
    }
    catch (...)
    {
    }
    std::string dev_id = getBlockDeviceId(data_path);
    if (getBlockDeviceType(dev_id) == BlockDeviceType::ROT && getBlockDeviceReadAheadBytes(dev_id) == 0)
        server.context()->addWarningMessage("Rotational disk with disabled readahead is in use. Performance can be degraded. Used for data: " + String(data_path));