Special Report

Disaster recovery technology guide

By Cath Everett, contributor

Implementing an effective disaster recovery plan is predominantly about defining and introducing suitable processes and procedures, but technology plays a key role in enabling execution.

Here's a quick guide to the technologies that can help you establish DR provision – with links to in-depth SearchStorage.co.uk content on each.

 

Archiving

What it does: Archiving tools store data no longer used in day-to-day activity but which must be retained, in some cases for decades and often to meet compliance rules. Archiving tools monitor data, migrate it to appropriate media (cheaper disk or tape) and in some cases maintain checks and controls on the integrity of the data for compliance reasons. Email is a major application covered by archiving tools and services.

DR role: Archiving is a complement to backup rather than a replacement for it. Backups of the archive are necessary, but archiving tools will allow restoration of the items in the archive, in some cases quite rapidly. By first restoring shells of files that can be accessed by users, the archiving tool prioritises the restoration of the full files that correspond to those users have requested.

Key vendors: Archiving software: Autonomy Zantaz, EMC, Mimosa Systems, Mimecast, Quest, Symantec. Hardware: EMC, Hewlett-Packard, Hitachi Data Systems

 

Backup

What it does: Backup tools copy data held in files or databases to secondary storage media. The aim is to ensure swift access to data to minimise downtime in case of an equipment failure or other disaster. Unlike with archiving software, it is often impossible to search easily for individual files and restore them from backups.

DR role: Copies of backups are recovered from storage media in the event of a disaster and can be restored to file and database systems running at a secondary DR site. The downside is that if disaster strikes, any data generated since the last backup took place will be lost. Backup activity is still the foundation of many DR plans.

Key vendors: Acronis, Asigra, BakBone, Commvault, Computer Associates, EMC, HP, IBM Tivoli, Symantec.

 

Continuous data protection

What it does: Continuous data protection (CDP) copies data from a source to a target system on an ongoing basis every time a change is made.

DR role: Employing CDP enables restoration of a system to the point where the last modification to data occurred, reducing the recovery point objective to almost zero. Because CDP keeps a record of every transaction that takes place, the most recent clean copy of a document can be recovered quickly if disaster strikes. The downside is that, because copies are not taken at regular timed intervals, it can be difficult to establish when the last one was taken without suitable management tools in place to help.

Key vendors: Atempo, Computer Associates, Double-Take, EMC, FalconStor, IBM Tivoli, InMage, Microsoft, Symantec

 

Snapshots

What it does: Snapshots are copies of data made from a source to a target system at pre-determined set points, whether that is every 10 minutes, once an hour or three times a day. Depending on their RPOs, many organisations substitute frequent snapshots for CDP.

DR role: Snapshotting enables the restoration of a system to the point where the last copy took place. The downside is that if disaster hits any data that was generated since the last snapshot occurred will be lost, as it would be with other traditional forms of backup.

Key vendors: All major storage vendors

 

Tape

What it does: For years, people have been backing up data by copying contents from their storage devices to a tape cartridge that can be stored offsite. If there is a backup disk failure or data gets deleted, missing data can be copied back from tape onto live storage. Tape backup has been losing ground to disk backup, which is faster and easier to restore from.

DR role: Although its role in backup has been diminished in favor of disk, tape still has a firm presence in DR. Backup to tape enables storage professionals to periodically copy data from a primary storage device to a tape library so it can be recovered if a failure occurs. Backup to tape is quick if optimized, and can be undertaken at the primary data centre with the media moved to a secure secondary site.

Key vendors: HP, IBM, Overland Storage, Quantum, SpectraLogic, Sun Microsystems, Tandberg Data

 

Disk

What it does: Disk-to-disk backup involves backing up data on a computer's hard disk to another disk in a storage array.

DR role: Backing up to disk is usually faster than tape backups because it's difficult to optimise tape streaming. Where disk-based backup does win hands down, however, is in restoration of files. It is easier and quicker to restore specific files from disk than tape in the event of a disaster. If network-connected, disk also removes the need to move multiple backup tapes back and forth between primary and secondary sites for recovery purposes.

 

Virtual tape library

What it does: A virtual tape library (VTL) is a staging device comprised of disk that mimics a tape library. Data backed up to a VTL can be replicated to other VTLs at a remote site or moved off to real tape for DR.

DR role: Employing a VTL lets organizations maintain the same backup and restore procedures for disk that they would employ for tape. Because VTL is disk-based, backup and recovery is quicker than with tape. One VTL can also replicate to other VTLs at a secondary location on a one-to-one or one-to-many basis, and users can decide which workloads require such site-to-site replication. This removes the need to move multiple backup tapes between primary and secondary sites for recovery purposes.

Key vendors: EMC, Data Domain, Hewlett-Packard, NetApp, Overland Storage, Quantum, Sepaton, Sun Microsystems, Tandberg Data

 

Data deduplication 

What it does: Data deduplication reduces the amount of data backed up by eliminating duplicate files and blocks. This reduces the amount of storage capacity required for backup by between 2:1 and 40:1 typically, depending on the type of data and frequency of backups.

The process works by ensuring that only the first unique instance of a piece of data is retained. Subsequent iterations of the data are replaced with a pointer to the original.

DR role: The technology can – depending on whether it is the inline or post-process flavour of deduplication - reduce the amount of data that has to be sent over a WAN, optimising bandwidth use when undertaking remote backup, replication and disaster recovery. Careful attention must be paid to restoration processes, as data must be rebuilt from its deduplicated state.

Key vendors: Copan, EMC, Data Domain, NEC, FalconStor, NetApp, Overland Storage, Quantum, Symantec.

 

 

Failover 

What it does: Failover refers to a way of configuring servers to enable redundant or standby secondary devices to take over from primary ones in the case of failure, abnormal termination of activity or scheduled downtime. This process can be undertaken manually or automatically depending on the setup.

DR role: A secondary site takes over critical operations after failover occurs, allowing the network to continue functioning following a disaster. When the primary server or site is ready to resume, operations fail back to the original location

Key vendors: CA, DoubleTake, Neverfail, SteelEye

 

This was first published in November 2009

 

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