ONTAP 9.14

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Volumes, qtrees, files, and LUNs

ONTAP serves data to clients and hosts from logical containers called FlexVol volumes. Because these volumes are only loosely coupled with their containing aggregate, they offer greater flexibility in managing data than traditional volumes.

You can assign multiple FlexVol volumes to an aggregate, each dedicated to a different application or service. You can expand and contract a FlexVol volume, move a FlexVol volume, and make efficient copies of a FlexVol volume. You can use qtrees to partition a FlexVol volume into more manageable units, and quotas to limit volume resource usage.

Volumes contain file systems in a NAS environment and LUNs in a SAN environment. A LUN (logical unit number) is an identifier for a device called a logical unit addressed by a SAN protocol.

LUNs are the basic unit of storage in a SAN configuration. The Windows host sees LUNs on your storage system as virtual disks. You can nondisruptively move LUNs to different volumes as needed.

In addition to data volumes, there are a few special volumes you need to know about:

  • A node root volume (typically “vol0”) contains node configuration information and logs.

  • An SVM root volume serves as the entry point to the namespace provided by the SVM and contains namespace directory information.

  • System volumes contain special metadata such as service audit logs.

You cannot use these volumes to store data.

Volumes that cannot be used to store data

FlexGroup volumes

In some enterprises a single namespace may require petabytes of storage, far exceeding even a FlexVol volume’s 100TB capacity.

A FlexGroup volume supports up to 400 billion files with 200 constituent member volumes that work collaboratively to dynamically balance load and space allocation evenly across all members.

There is no required maintenance or management overhead with a FlexGroup volume. You simply create the FlexGroup volume and share it with your NAS clients. ONTAP does the rest.

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