About Data ONTAP

Data ONTAP overview

You administer the filer by using Data ONTAP commands either directly or through the FilerView graphical user interface.

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 handles four types of data management:

Data storage
Data organization
Data access
Data migration

Data storage management

Data ONTAP stores data on disks in disk shelves. When filer volumes are created and these disks are assigned to them, Data ONTAP groups these disks into RAID groups within that volume. The RAID groups are organized to provide parity protection against data loss within each group due to disk or sector failure. RAID and disk-related terms 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 ensures data preservation and file access even if one disk or two disks in a RAID group are damaged.	You can specify the level of RAID protection (RAID 4 or RAID DP) for each volume on the filer.
RAID group	A set of data disks and one or two parity disks, grouped to provide parity protection against data loss within that group due to disk or sector failure. Data ONTAP supports up to 400 RAID groups per filer or cluster.	You can control the size of a RAID group and the level of RAID protection. 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 if a disk fails.
Parity disk	Contains information that Data ONTAP uses to reconstruct data if a data disk fails. Depending on the level of RAID protection enabled, each RAID group uses one parity disk (for single disk failure protection under RAID 4) or two parity disks (for double disk failure protection under RAID DP).
Hot spare disks	Replace failed data disks automatically with reconstructed data.
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 into directories, and you organize directories into file systems, which are known as volumes. You can also organize directories into special directories called qtrees. Major data organization concepts that are particular to filers are explained in the following table.

Data organization concept	Explanation	Data organization administrative actions
Volume	One or more independent file systems contained in a filer.	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

Explanation

Data organization administrative actions

Volume

One or more independent file systems contained in a filer.

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 takeover
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