Traditional and FlexVol volumes

About traditional and FlexVol volumes

Volumes are file systems that hold user data that is accessible via one or more of the access protocols supported by Data ONTAP, including NFS, CIFS, HTTP, WebDAV, FTP, FCP and iSCSI. You can create one or more snapshots of the data in a volume so that multiple, space-efficient, point-in-time images of the data can be maintained for such purposes as backup and error recovery.

Each volume depends on its containing aggregate for all its physical storage, that is, for all storage in the aggregate's disks and RAID groups. A volume is associated with its containing aggregate in one of the two following ways:

A traditional volume is a volume that is contained by a single, dedicated, aggregate; it is tightly coupled with its containing aggregate. The only way to grow a traditional volume is to add entire disks to its containing aggregate. It is impossible to decrease the size of a traditional volume. The smallest possible traditional volume must occupy all of two disks (for RAID4) or three disks (for RAID-DP).
No other volumes can get their storage from this containing aggregate.

All volumes created with a version of Data ONTAP earlier than 7.0 are traditional volumes. If you upgrade to Data ONTAP 7.0 or later, your volumes and data remain unchanged, and the commands you used to manage your volumes and data are still supported.
A FlexVol volume (sometimes called a flexible volume) is a volume that is loosely coupled to its containing aggregate. Because the volume is managed separately from the aggregate, you can create small FlexVol volumes (20 MB or larger), and you can increase or decrease the size of FlexVol volumes in increments as small as 4 KB.
A FlexVol volume can share its containing aggregate with other FlexVol volumes. Thus, a single aggregate can be the shared source of all the storage used by all the FlexVol volumes contained by that aggregate.

Data ONTAP automatically creates and deletes Snapshot copies of data in volumes to support commands related to Snapshot technology. You can accept or modify the default Snapshot copy schedule. For more information about Snapshot copy, see the Data Protection Online Backup and Recovery Guide.

Note
FlexVol volumes have different best practices, optimal configurations, and performance characteristics compared to traditional volumes. Make sure you understand these differences and deploy the configuration that is optimal for your environment.

For information about deploying a storage solution with FlexVol volumes, including migration and performance considerations, see the technical report Introduction to Data ONTAP Release 7G (available from the NetApp Library at http://www.netapp.com/tech_library/ftp/3356.pdf).

Limits on how many volumes you can have

You can create up to 200 FlexVol and traditional volumes on a single storage system. In addition, the following limits apply.

Traditional volumes

You can have up to 100 traditional volumes and aggregates combined on a single storage system.

FlexVol volumes

The only limit imposed on FlexVol volumes is the overall system limit of 200 for all volumes.

For clusters, these limits apply to each node individually, so the overall limits for the pair are doubled.

Types of volume operations

The volume operations described in this chapter fall into three types:

Traditional volume operations
These are RAID and disk management operations that pertain only to traditional volumes.
- Creating traditional volumes
- Physically transporting traditional volumes
FlexVol volume operations
These are operations that use the advantages of FlexVol volumes, so they pertain only to FlexVol volumes.
General volume operations
These are operations that apply to both FlexVol and traditional volumes.