# Import Mode (Import Mode) of TiDB Lightning

__*Lightning import mode*__

| Backend | Physical Import Mode | Logical Import Mode |
| :-- | :-- | :-- |
| Speed | Fast (~500 GB/hr) | Slow (~50 GB/hr) |
| resource usage | high | low |
| Used Network Bandwidth | High | Low |
| Does the import satisfy ACID | No | Yes |
| target table | must be empty | may not be empty |
| Support for TiDB cluster versions | >= v4.0.0 | All |
| Can TiDB provide services | No | Yes |

-------------------------------------------------------------
Physical Import Mode: TiDB Lightning first encodes the data into key-value pairs and stores them in a local temporary directory, uploads these key-value pairs to various TiKV nodes, and finally calls the TiKV Ingest interface to insert the data into TiKV's rocksDB. If used to initialize the import, give preference to the Physical Import Mode mode, which has a high import speed.

Logical Import Mode: TiDB Lightning first encodes the data into SQL, and then directly runs these SQL statements to import the data. You should use the Logical Import Mode mode if the cluster you want to import is a production environment online cluster, or if the target table you want to import already contains data.

Do not use the Physical Import Mode mode to import data into a TiDB cluster that is already in production, as this will have a serious impact on online business.
By default, you should not launch multiple TiDB Lightning instances at the same time to import data to the same TiDB cluster. Instead, consider using the parallel import feature.
When using multiple TiDB Lightning to import to the same target, do not mix different backends; for example, you cannot use both Physical Import Mode and Logical Import Mode to import the same TiDB cluster.