You can have a maximum of 100 FlexCache volumes on a storage system. In addition, there are certain features of Data ONTAP that are not available on FlexCache volumes, and others that are not available on volumes that are backing FlexCache volumes.
You cannot use the following Data ONTAP capabilities on FlexCache volumes (these limitations do not apply to the origin volumes):
- Client access using any protocol other than NFSv2 or NFSv3
- Client access using IPv6
- Compression (compressed origin volumes are supported)
- Snapshot copy creation
- SnapMirror (qtree or volume)
- FlexClone volume creation
- The ndmp command
- Volume copy
- Creation of FlexCache volumes in any vFiler unit other than vFiler0
- Creation of FlexCache volumes in the same aggregate as their origin volume
- Mounting the FlexCache volume as a read-only volume
If your origin volume is larger than 16 TB, the output of the df command on the caching system will show "---" for the size information about the origin volume. To see the size information for the origin volume, you must run the df command on the origin system.
You cannot use the following Data ONTAP capabilities on FlexCache origin volumes or storage systems without rendering all of the FlexCache volumes backed by that volume or storage system unusable:
Note: If you want to perform these operations on an origin system, you can destroy the affected FlexCache volumes, perform the operation, and re-create the FlexCache volumes. However, the FlexCache volumes will need to be repopulated.
- You cannot move an origin volume between vFiler units or to vFiler0 by using any of the following commands:
- vfiler move
- vfiler add
- vfiler remove
- vfiler destroy
You can use SnapMover (vfiler migrate
) to migrate an origin volume without having to re-create FlexCache volumes backed by that volume.
Origin volumes can be owned by any vFiler unit.
- You cannot use a FlexCache origin volume as the destination of a snapmirror migrate command.
- You cannot change the language of the origin volume if the change causes the underlying character set to change, or if the new language is not available on the caching system.
For example, you can change the language of the origin volume from English to US English. However, if you want to change the language from English to a language that uses a different character set, such as Japanese, then you need to destroy and re-create all of the FlexCache volumes backed by the origin volume.
- Qtrees contained by the origin volume that belong to a vFiler unit other than the vFiler unit that owns the origin volume are not accessible to a FlexCache volume.
For example, suppose that volume vol1 is owned by vFiler0 but qtree1, which is contained by vol1, is owned by another vFiler unit. FlexCache volumes created with vol1 as the backing volume will not be able to access the data contained in qtree1.
- If your origin volume is on a system running a version of the Data ONTAP 10.0 release family, and any node in the origin cluster is down, the FlexCache volume will not be able to establish a connection with the origin volume.
- If the origin volume contains Snapshot copies, the Snapshot data is not written to disk (cached). Snapshot data is stored only in the in-memory buffer cache of the caching filer.