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Comparison between volume SnapMirror and qtree SnapMirror

You can configure SnapMirror replication for either entire volumes or individual qtrees on a volume. You should consider the differences between the two options.

The following table describes the characteristics of SnapMirror replication:

Volume SnapMirror Qtree SnapMirror
Synchronous or asynchronous replication is supported for volumes. Only asynchronous replication is supported for qtrees.
Destination volume is read-only. Destination qtree is read-only. However, the volume on which the qtree is located must be online and writable.
Source and destination volumes must both be either traditional volumes or FlexVol volumes. Source and destination qtrees can be on any type of volumes, traditional volumes or FlexVol volumes.
Replicates Snapshot copies of a source volume and all its qtrees, to the destination volume Replicates only the contents of an individual qtree to a destination
You need to set a destination volume to restricted, read-only status, before setting it up for replication. The destination volume for qtree replication is writable, and must not be read-only.
Replication of a volume on the destination takes up the space allocated to the source volume, irrespective of how much of the volume is used for storing data. If you need to mirror only the data stored on an individual qtree, then SnapMirror replication of that individual qtree uses slightly more disk space and directories on the destination qtree than the source qtree.
Replication can be set up to a destination volume from only one source volume. This implies that one destination volume cannot be used for replicating multiple source volumes. Replication can be set up for a maximum of 255 qtrees on any one volume.
Block-for-block replication

It transfers the file system verbatim. Therefore, older releases of Data ONTAP cannot understand file system transfers from a later release of Data ONTAP.

Logical replication

All the files and directories in the source file system are created in the destination file system. Therefore, you can replicate data between a storage system running an older version of Data ONTAP and a storage system running a newer version.

Note: If the source file system contains a file type that cannot be represented on the destination file system, the replication will fail. For example, Data ONTAP 7.0 supports files up to 16 TB in size, whereas earlier versions of Data ONTAP support files up to 4 TB. If the source system is running Data ONTAP 7.0, the qtree you want to replicate contains a file greater than 4 TB, and the destination system is running an earlier version of Data ONTAP, the replication will fail.