# Server version and backup version comparison

A *MySQL* change to a feature, such as the structure of a redo log
record, can cause older versions of **Percona XtraBackup** to fail. To
ensure that you can back up and restore your data, use a **Percona
XtraBackup** version that is equal to or above your source server version.

!!! admonition "See also"
   
    [How XtraBackup works](https://docs.percona.com/percona-xtrabackup/8.0/how_xtrabackup_works.html)

*Percona XtraBackup* 8.0.21 adds the `--no-server-version-check` option.
Before the backup starts, XtraBackup compares the source system version to
the *Percona XtraBackup* version. If the source system version is greater
than the XtraBackup version, XtraBackup stops the backup and returns an
error message. This comparison prevents a failed backup or a corrupted
backup due to source system changes.

The parameter checks for the following scenarios:

* The source system and the PXB version are the same, the backup proceeds

* The source system is less than the PXB version, the backup proceeds

* The source system is greater than the PXB version, and the parameter is not overridden, the backup is stopped and returns an error message

* The source system is greater than the PXB version, and the parameter is  overridden, the backup proceeds

Explicitly adding the `--no-server-version-check` parameter, like the
example, overrides the parameter and the backup proceeds.

```{.bash data-prompt="$"}
$ xtrabackup --backup --no-server-version-check --target-dir=$mysql/backup1
```

When you override the parameter, the following events can happen:

* Backup fails

* Creates a corrupted backup

* Backup successful