Terms

Array group

On the storage subsystem, the arrangement of disks in the back-end that together form the defined RAID level. An array group might also be referred to as a parity group or an ECC group.

Channel adapter (CHA)

Includes the Client-Host Interface Processor (CHIP). The interface between the system and hosts or servers on an open system.

Cluster

Two gFilers directly connected to each other. This type of deployment provides redundancy in case one gFiler in the cluster becomes unavailable. Each of the gFilers in the cluster might be referred to as a node--a local node or a partner node.

LDEV

Logical Device: Unit of capacity, defined at format time, that is used as capacity placeholder until it is mapped as a LUN.

LUN

Logical Unit Number (LUN). An area on the storage subsystem that is available for a gFiler or non-gFiler host to read data from or write data to.

Mapping or port definitions

The task of assigned LDEVs, by address, to Fibre Channel ports.

Neighborhood

The number of nodes that can see each others' LUNs. When you configure LUNs on the storage subsystem, you identify the hosts in particular neighborhoods.

Node

In a gFiler cluster, either the local or partner gFiler.

Parity group

Same as Array Group or ECC Group.

RAID protocols supported

gFilers support storage subsystems that use the RAID-1, RAID-5, and RAID-10 protocols, although the gFilers do not themselves use RAID-1, RAID-5, or RAID-10. The following illustration provides a conceptual view of RAID-0 used on the gFiler and the RAID-1, RAID-5, and RAID-10 storage subsystems.

The gFiler stripes across LUNs in RAID-0, thereby maximizing performance because it is using more spindles. Another benefit of the gFiler using RAID-0 for striping across LUNs is that you can add LUNs to a NetApp volume.

There is no need for the gFiler to provide disk protection. The LUNs are already protected with the redundancy provided by RAID-1, RAID-5, and RAID-10 on the storage systems.

Note
NetApp filers use the RAID-4 protocol for disk protection. The RAID-4 protocol is not needed for gFilers because the storage subsystems provide disk protection. Most of the disk information in the Data ONTAP documentation does not apply to the gFiler because it is about RAID-4.

RAID group

A NetApp volume is composed of one or more NetApp RAID (Redundant Array of Independent Disks) groups. From the perspective of gFilers, Data ONTAP uses RAID groups to determine where to allocate data to the LUNs. (From the perspective of NetApp filers, a RAID group is composed of one or more data disks, across which client data is striped and stored, plus one or two parity disks that ensure data recoverability even if as many as two disks within the RAID group fail.)

Each RAID group belongs to only one volume (physical file system); you cannot assign a RAID group to more than one volume.

Volume

In Data ONTAP, volumes are the primary means of organizing and managing data. You can think about a volume as a container for storing data. You identify the collection of LUNs that are to be in the volume (where collection could mean only one LUN); those LUNs provide the capability for data storage. You manage data storage by managing volumes through the Data ONTAP system administration interface.

The capability of associating LUNs with volumes provides you a great deal of flexibility for data management. For example, you could create volumes to accommodate your users if they speak more than one language; you could create one volume for data in French and another for data in German. Alternatively, you can include all LUNs in one volume, the root volume that the gFiler setup process creates. The gFiler Gateway Series Software Installation, Setup, and Management Guide contains information about volume management.

Relationship of RAID groups to volumes

A NetApp volume is composed of one or more NetApp RAID groups.

The following illustration shows the components of a volume from the filer perspective--each volume is made up of one or more RAID groups, which are made up of one or more disks.

The following illustration shows the concept of the components of a volume from the perspective of a storage subsystem--each NetApp volume is made up of one or more LUNs in one or more RAID groups.