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openshift-docs/modules/configuring-rsync-for-direct-volume-migration.adoc
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// Module included in the following assemblies:
//
// migration_toolkit_for_containers/mtc-direct-migration-requirements.adoc
:_mod-docs-content-type: CONCEPT
[id="configuring-rsync-for-direct-volume-migration_{context}"]
= Rsync configuration for direct volume migration
Direct Volume Migration (DVM) in {mtc-short} uses Rsync to synchronize files between the source and the target persistent volumes (PVs), using a direct connection between the two PVs.
Rsync is a command-line tool that allows you to transfer files and directories to local and remote destinations.
The `rsync` command used by DVM is optimized for clusters functioning as expected.
The `MigrationController` CR exposes the following variables to configure `rsync_options` in Direct Volume Migration:
[width="100%",cols="15%,15%,20%,50%",options="header",]
|===
|Variable
|Type
|Default value
|Description
|`rsync_opt_bwlimit`
|int
|Not set
|When set to a positive integer, `+--bwlimit=<int>+` option is added to Rsync command.
|`rsync_opt_archive`
|bool
|`true`
|Sets the `+--archive+` option in the Rsync command.
|`rsync_opt_partial`
|bool
|`true`
|Sets the `+--partial+` option in the Rsync command.
|`rsync_opt_delete`
|bool
|`true`
|Sets the `+--delete+` option in the Rsync command.
|`rsync_opt_hardlinks`
|bool
|`true`
|Sets the `+--hard-links+` option is the Rsync command.
|`rsync_opt_info`
|string
|`COPY2`
`DEL2`
`REMOVE2`
`SKIP2`
`FLIST2`
`PROGRESS2`
`STATS2`
|Enables detailed logging in Rsync Pod.
|`rsync_opt_extras`
|string
|Empty
|Reserved for any other arbitrary options.
|===
* Setting the options set through the variables above are _global_ for all migrations. The configuration will take effect for all future migrations as soon as the Operator successfully reconciles the `MigrationController` CR. Any ongoing migration can use the updated settings depending on which step it currently is in. Therefore, it is recommended that the settings be applied before running a migration. The users can always update the settings as needed.
* Use the `rsync_opt_extras` variable with caution. Any options passed using this variable are appended to the `rsync` command, with addition. Ensure you add white spaces when specifying more than one option. Any error in specifying options can lead to a failed migration. However, you can update `MigrationController` CR as many times as you require for future migrations.
* Customizing the `rsync_opt_info` flag can adversely affect the progress reporting capabilities in {mtc-short}. However, removing progress reporting can have a performance advantage. This option should only be used when the performance of Rsync operation is observed to be unacceptable.
[NOTE]
====
The default configuration used by DVM is tested in various environments. It is acceptable for most production use cases provided the clusters are healthy and performing well.
These configuration variables should be used in case the default settings do not work and the Rsync operation fails.
====