Data explosion puts critical data recovery process in jeopardy

Johannesburg, 28 Jan 2004
Read time 6min 00sec

Exponential data growth, 24x7 information accessibility, rising downtime costs and restricted IT budgets are all placing organisations under increasing pressure to protect and recover business-critical information in less time and at lower cost.

Today`s IT environments, with strong disaster recovery requirements, demand multiple copies of data with a lifecycle that takes storage media from onsite to offsite locations.

In addition, recovery service levels and the need to provide a comprehensive onsite/offsite data protection plan increase the pressure on IT staff to deliver a multi-faceted backup solution within the framework of a limited budget.

Multi-step process

Effective data protection today demands a multi-step process: the first step centres on near-line storage for rapid recovery during the initial "window" period following backup. The second involves the cloning of the backup image to removable, long-term media (usually tape media) for purposes of cost-effective extended storage.

The last stage is to physically relocate the tape media to an offsite location for disaster recovery purposes.

Tape library emulation

The new-generation technology developed to achieve these goals is the emulation of tape library functionality on RAID-protected disk-based systems.

Simply put, inserting disk or other faster-access/higher-reliability technologies into the existing (tape-based) storage architectures adds speed, reliability and flexibility to a firm`s data protection capabilities.

This approach optimises an organisation`s existing IT investment in both backup hardware and software and minimises the impact on existing backup operational procedures.

The pioneers of this development are Quantum and Legato. Together they have developed what they maintain is a strong example of this new breed of "enhanced backup" systems.

Their multi-faceted data protection solution is designed to minimise required changes to pre-existing architectures and processes.


Central to the solution is the ability to make duplicate copies of the data through a process called "cloning". While cloning ensures that the copies of the data are accurate, it also keeps track of the information necessary to browse and recover the data.

This process differs significantly from simple tape duplication, and is centred on a disk-based emulation of a tape library.

The solution makes use of the inherent strengths of disk (quick access, high-speed data transfer and RAID protection) to improve backup target functions. Through the cloning process, the backup target data can easily copy to the disk library, which uses its strengths (low cost, ability to write large block sizes, removable media and archival stability) to concentrate on what it does best - archival data storage.

Furthermore, since a copy of the most recent backup is still available on the disk-based enhanced backup system, recovery to the most recent point in time can occur in a minimal amount of time.

Step one

The first step to building a comprehensive onsite/offsite backup solution is to implement the initial backup. The disk library concept, with the elimination of tape media cartridge handling and management, makes administration simpler. This is underlined by increased seek speeds and the lower incidents of media failure associated with disk-based systems.

Service levels for data restore increase as management requirements decrease, since error due to operator mistakes are less likely with less handling. And since a RAID configuration is employed, with its redundant hardware architecture, security is enhanced.

Step two

With data safely stored on disk, the backup image must be transferred to removable media for offsite storage purposes. The data is cloned to a tape. This offsite copy gives the option of restoring from either the primary or the offsite location.

In this step, the system enables the administrator to clone data automatically at the end of the initial backup. Two options are then available; either to immediately remove the clone, or clone manually through the use of a script at an appropriate time.

Strategic considerations

The amount of data to be backed up drives any backup strategy. This information is necessary to determine amount of storage and removable media needed.

In the described solution, the amount of data directly affects how cloning is performed. The amount of capacity on a disk drive is fixed and is not required to be removable since it provides large quantities of disk space in a small footprint. The only way to regain space on this equipment is to overwrite previously written backup images.

The data capacity requirement helps determine the number of disk drives required, as well as the size of the tape library unit needed for cloning. Due to characteristics of RAID, the capacity required to protect the disks consumes various amounts of space. Useable space versus total space can also vary due to hardware redundancy requirements.

Also worthy of consideration is the prioritisation of data. This is important when determining the data protection lifecycle for a given set of data, since the priority determines restore service levels, length of backup image retention, and onsite/offsite location of backup image.

High priority data is that which supports the key strategic processes within the business. Data might have high priority due to industry regulations or company policy on retention requirements.

For example, some organisations are required to retain e-mail under regulatory or statutory requirements.

New regulations raise the bar on record-keeping for many companies. Data retention requirements must be identified for each data set backed up. Similar retention and priority data sets should be kept in the same pools because data retention determines when media will be free for recycling.

Key consideration

Key considerations include the restore service level required. This refers to the window of time allowed between the end-user request for recovery and the restoration of the data to its original location.

The strategic importance of each data set determines the proper restore service level, which can be described as high, medium, or low.


Finally, disaster recovery and long-term storage needs dictate the need for off-site storage requirements. Offsite practices can exploit cloning to get the backup image from near-line storage to removable media, while also keeping it on near-line storage for quick recovery.

Immediate deployment of off-site copies to off-site storage is necessary for purposes of recovering high priority data from a site disaster.

This offsite operation can be also accomplished using a WAN connection between the primary location and the offsite location.

However, the user needs to question the amount of data to be cloned relative to the bandwidth available to accomplish this. In SA, it is more practical to clone locally and then courier the tape media to the desired offsite location.

Editorial contacts
HMC Corporate Communications Mary Siemers (011) 463 4611
Channel Data Amit Parbhucharan (011) 235 7744
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