SnapVault overview

What is SnapVault

SnapVault is a disk-based storage backup feature of Data ONTAP that enables data stored on multiple storage systems to be backed up to a central, secondary storage system quickly and efficiently as read-only Snapshot copies. In event of data loss or corruption on a storage system, backed up data can be restored from the SnapVault secondary system with less downtime and less of the uncertainty associated with conventional tape backup and restore operations.

Terminology

This chapter uses the following terms to describe the SnapVault feature:

Primary storage system--a system whose data is to be backed up
Secondary storage system--a storage system or NearStore to which data is backed up
Primary system qtree--a qtree on a primary storage system whose data is backed up to a secondary qtree on a secondary storage system
Secondary system qtree--a qtree on a secondary storage system to which data from a primary qtree on a primary storage system is backed up
Open Systems platform--a server running AIX, Solaris, HP-UX, Linux, Windows NT, Windows 2000, or Windows 2003, whose data can be backed up to a SnapVault secondary storage system
Open Systems SnapVault agent--a software module that enables the system to back up its data to a SnapVault secondary storage system
SnapVault relationship--the backup relationship between a qtree on a primary system or a directory on an Open Systems primary platform and its corresponding secondary system qtree
SnapVault Snapshot copy--the backup images that SnapVault creates at intervals on its primary and secondary storage systems. SnapVault Snapshot copies capture the state of primary qtree data on each primary system. This data is transferred to secondary qtrees on the SnapVault secondary system, which creates and maintains versions of Snapshot copies of the combined data for long-term storage and possible restore operations.
SnapVault Snapshot basename--a name that you assign to a set of SnapVault Snapshot copies through the snapvault snap sched command. As incremental Snapshot copies for a set are taken and stored on both the primary and secondary storage systems, the system appends a number (0, 1, 2, 3, and so on) to the basenames to track the most recent and earlier Snapshot updates.
SnapVault baseline transfer--an initial complete backup of a primary storage qtree or an Open Systems platform directory to a corresponding qtree on the secondary storage system
SnapVault incremental transfer--a followup backup to the secondary storage system that contains only the changes to the primary storage data between the current and last transfer actions

Advantages of SnapVault

The SnapVault disk-based backup and restore system enables you to do the following:

Browse backed-up files online
Schedule fast, frequent, efficient backup of large amounts of data
Carry out fast, flexible, selective, and simple data restore operations
Minimize media consumption and system overhead through incremental backup
If tape backup is necessary, offload the tape backup task from the primary storage systems to the Snapshot secondary storage system, which centralizes the operation and saves resources
Configure and maintain a single system for backing up data stored on multiple platforms: Data ONTAP, AIX, Solaris, HP-UX, Linux, Windows NT server, Windows 2000 server, or Windows 2003 server systems

What data gets backed up and restored

The data structures that are backed up and restored through SnapVault depend on the primary storage system.

On Data ONTAP storage systems, the qtree is the basic unit of SnapVault backup and restore.
SnapVault backs up specified qtrees on the primary storage system to associated qtrees on the SnapVault secondary storage system. If necessary, data is restored from the secondary qtrees back to their associated primary qtrees.
On Open System storage platforms, the directory is the basic unit of SnapVault backup.
SnapVault backs up specified directories from the native system to specified qtrees in the SnapVault secondary storage system. If necessary SnapVault can restore an entire directory or a specified file to the Open System storage platform.

Primary storage qtrees from multiple storage systems, or primary directories from multiple Open Systems storage platforms, can all be backed up to associated qtrees on a single SnapVault secondary volume.

Basic SnapVault deployment

The basic SnapVault backup system deployment consists of the following components.

Primary storage systems

Primary storage systems are the Data ONTAP and Open Systems primary storage platforms to be backed up.

On primary storage systems, SnapVault backs up primary qtree data, non-qtree data, and entire volumes to qtree locations on the SnapVault secondary storage system.
Supported Open Systems storage platforms include Windows NT servers, Windows 2000 servers, Solaris servers, AIX servers, Linux servers, and HP-UX servers. On Open Systems storage platforms, SnapVault can back up directories to qtree locations on the secondary storage system. SnapVault can restore directories and single files.

Secondary storage system

The SnapVault secondary storage system is the central disk-based unit that receives and stores backup data from the storage system as Snapshot copies. Any storage system can be configured as a SnapVault secondary storage system; however, the recommended hardware platform is a NearStore system.

The following figure shows a basic SnapVault deployment.

Primary to secondary to tape backup variation

A common variation to the basic SnapVault backup deployment adds a tape backup of the SnapVault secondary storage system. This deployment might serve two purposes:

It enables you to store an unlimited number of network backups offline while keeping your most recent backups available online in secondary storage, if necessary, for quick restoration. If you run a single tape backup off the SnapVault secondary storage system, your storage platforms are not subject to the performance degradation, system unavailability, and complexity of direct tape backup of multiple systems.
It can be used to restore data to a SnapVault secondary storage system in case of data loss or corruption on that system.

The following figure shows a basic SnapVault deployment plus tape backup.

Note
Some Windows NT and UNIX attributes are not preserved using this method; notably, Windows NT sparse files, Windows NT EFS Encrypted Data, and UNIX access control lists (ACLs).

Primary to secondary to SnapMirror variation

Another variation to the basic SnapVault deployment protects Snapshot copies stored on SnapVault secondary storage against problems with the secondary storage system itself. The data backed up to SnapVault secondary storage is mirrored to a unit configured as a SnapMirror partner, or destination. If the secondary storage system fails, the data mirrored to the SnapMirror destination can be converted to a secondary storage system and used to continue the SnapVault backup operation with a minimum of disruption.

The following figure shows a SnapVault deployment with a SnapMirror backup.

How SnapVault backup of storage systems works

The process of SnapVault backup of storage system qtrees is as follows:

Starting the baseline transfers

In response to command line input, the SnapVault secondary storage system requests initial base transfers of qtrees specified for backup from a primary storage volume to a secondary storage volume. These transfers establish SnapVault relationships between the primary and secondary qtrees.
Each primary storage system, when requested by the secondary storage system, transfers initial base images of specified primary qtrees to qtree locations on the secondary storage system.

Making scheduled incremental transfers

Each primary storage system, in response to command line input, creates sets of scheduled SnapVault Snapshot copies (which, for tracking purposes, you might name according to frequency, for example, "sv_hourly," "sv_nightly," and so on) of the volumes containing the qtrees to be backed up.
For each Snapshot set, SnapVault saves the number of primary storage Snapshot copies you specify and assigns each Snapshot a version number (0 for most current, 1 for second most recent, and so on).
The SnapVault secondary storage system, in response to command line input, carries out a specified set of scheduled data transfer and Snapshot actions. For each of its secondary qtrees on a given volume, SnapVault retrieves, from the Snapshot data of each corresponding primary qtree, the incremental changes to the primary qtrees made since the last data transfer.
Then SnapVault creates a volume Snapshot copy of the changes in the secondary qtrees.

For each transfer and Snapshot set, SnapVault saves the number of secondary storage Snapshot copies that you specify and assigns each Snapshot copy a version number (0 for most current, 1 for second most recent, and so on).

Restoration upon request

If data needs to be restored to the primary storage system, SnapVault transfers the specified versions of the qtrees back to the primary storage system that requests them.

The following diagram illustrates SnapVault functionality.

How SnapVault backup of Open Systems platforms works

SnapVault backup of Open Systems platform directories works as follows:

Starting the baseline transfers

In response to command line input, the SnapVault secondary storage system requests from an Open Systems platform initial baseline image transfers of directories specified for backup. These transfers establish SnapVault relationships between the Open Systems platform directories and the SnapVault secondary qtrees.
Each Open Systems platform, when prompted by the secondary storage system, transfers initial base images of specified directories to qtree locations on the secondary storage system.

Scheduling incremental transfers

The SnapVault secondary storage system, in response to command line input, follows a set of scheduled data transfers (to which, for tracking purposes, you can assign names like "sv_hourly," "sv_nightly," and so on). To each secondary qtree on a given volume, from a corresponding primary directory on the Open Systems storage platform, SnapVault transfers the files that have been added or modified since the previous data transfer.
For each set of scheduled data transfers, SnapVault creates a set of incremental Snapshot copies that capture the changes to the secondary qtrees after each transfer.

For each set of Snapshot copies, the SnapVault secondary storage system saves the number of secondary storage Snapshot copies you specify and assigns each Snapshot copy in the set a version number (0 for most current, 1 for second most recent, and so on).

Restore upon request

If directory or file data needs to be restored to the Open Systems storage platform, SnapVault retrieves the data from one of the retained Snapshot copies and transfers the data back to the Open Systems storage platform that requests it.

Maximum number of simultaneous SnapVault backups

SnapVault backups have the same limit of simultaneous replications that SnapMirror replications have. See Maximum number of simultaneous replication operations.