About Data ONTAP

Data ONTAP overview

You administer the filer using Data ONTAP commands. Data ONTAP uses only commands and files that are relevant to file service administration. Data ONTAP contains no extraneous utilities, such as text editors.

Data ONTAP manages data in four ways:

Data storage management
Data organization management
Data access management
Data migration management

Data storage management

Data ONTAP stores data on disks in disk shelves. Disks are organized into RAID groups, and RAID groups are organized into volumes. These items are explained in the following table, along with what aspects of them you can administer.

Data storage concept	Explanation	Storage administrative actions
RAID (redundant array of independent disks)	A feature that enables file access even if one disk in a RAID group is damaged.	--
RAID group	A RAID group consists of a parity disk, up to 52 data disks before Data ONTAP 5.0 and 28 data disks in Data ONTAP 5.0 and later, and optional spare disks. Data ONTAP supports up to 150 RAID groups per filer or cluster.	You can control the size of a RAID group. This enables you to customize backups and disk failure recovery.
Data disks	Hold the data that clients access	You can control the number of data and spare disks that a filer can use. This enables you to manage recovery when disks fail.
Parity disk	Contains information that Data ONTAP uses to reconstruct data when data disks fail. Each RAID group includes one parity disk.
Spare disks	Replace failed data disks automatically with reconstructed data.
Volumes	Pools of storage composed of multiple disks that store client data. A filer can support from 1 to 200 volumes.	You can specify the size of a volume, add disks to it, copy volumes, and control the number of RAID groups in a volume. This gives you flexibility in managing data storage tasks such as backups and restores, and enables you to customize volumes.
Logical unit numbers (LUNs)	Logical units of storage, each of which is identified by a number, used in a storage area network (SAN) environment.	You can create LUNs within volumes and specify the size of a LUN.

Data organization management

Data is organized in files, which are the smallest unit of data management. Users organize files within directories, and you organize directories within file systems called volumes. You can also organize directories into special directory types called qtrees. Major data organization concepts that have special meaning for filers are described in the following table.

Data organization concept	Description	Data organization administrative actions
Volume	An independent file system	You can specify the following features for a volume: A security style, which determines whether a volume can contain files that use UNIX security, files that use NT file system (NTFS) security, or both types of files Whether it uses CIFS oplocks Disk space and file limits This enables you to customize volumes for the needs of your users.
qtree	A special subdirectory of the root directory of a volume. It has the following special attributes: A security style A CIFS oplocks setting Disk space and file limits	You can specify the following features for a qtree: A security style like that of volumes Whether it uses CIFS oplocks Disk space and file limits This enables you to customize areas for projects and to keep users and projects from monopolizing resources.

Data organization concept

Description

Data organization administrative actions

Volume

An independent file system

You can specify the following features for a volume:

A security style, which determines whether a volume can contain files that use UNIX security, files that use NT file system (NTFS) security, or both types of files
Whether it uses CIFS oplocks
Disk space and file limits

This enables you to customize volumes for the needs of your users.

qtree

A special subdirectory of the root directory of a volume. It has the following special attributes:

A security style
A CIFS oplocks setting
Disk space and file limits

You can specify the following features for a qtree:

A security style like that of volumes
Whether it uses CIFS oplocks
Disk space and file limits

This enables you to customize areas for projects and to keep users and projects from monopolizing resources.

Data access management

Data ONTAP manages access to data by performing the following operations:

Checks file access permissions against file access requests.
Checks write operations against file and disk usage quotas that you set.
Takes snapshots and makes them available so that users can access deleted or overwritten files. Snapshots are read-only copies of the entire file system.

Data ONTAP enables you to perform the following actions:

Manage network connections
Manage protocols
Configure pairs of filers into clusters for failover
Dump data to tape and restore it to the filer
Copy volumes
Mirror volumes (synchronously and asynchronously)
Create vFiler^TM units

Data migration management

Data ONTAP manages data migration by means of

Snapshots
Asynchronous mirroring
Synchronous mirroring
Backup to tape
Volume copy