Why File-based System Backup is your Best Bet
File-based, Full System Backups Create Advantages Over Image-based Backups

File-based backups used for system recovery have been around for years. And, until recently, file-based meant a long, painstaking, manual process capable of turning off even the most meticulous system administrator. Image-based backups, then, seemed to solve this problem by eliminating the need to deal with recreating partitions, filesystems, volume groups or other details related to the system's storage configuration. In an image-based restore, the storage configuration and data from the original system are restored as a whole to the new system. While this method produced fast recovery times, Linux administrators began to realize disk image backup was more of an alternative method with its own set of problems and limitations than an answer to the challenges of manual, file-based backup.

Limitations to Disk Image Backup
Since disk image backups make no distinction between files and instead backup the hard drive as a group of sectors, bare-metal recovery can be quick and easy by simply rewriting a duplicate image onto a new, identical disk drive. A fine solution, as long as the old system and new system are indeed identical in types, sizes, locations- basically the exact same hardware. Any differences in hardware, however, could render an image backup unusable.

Many system administrators know first-hand the frustration caused by the inflexibility of image-based backup. "What I hear time and time again from clients is that they switched from image-based backup to file-based because of the limitations they encountered when trying to restore a backup onto different hardware." said Manuel Altamirano, Storix Software Director of Sales and Marketing. "Administrators assume they will have access to identical hardware after a disaster or for migration when the time comes. Unfortunately, so often this is not the case. Companies are left with unplanned, excessive downtime."

Even more advanced disk image backup products, that offer alterations to disk partition tables, still fail to understand more advanced and increasingly common storage configuration tools such as the Logical Volume Manager (LVM) or Software RAID (meta-disks) that also must be altered to match new hard disk configuration before data can be restored. In these cases, users must manually alter and build the configuration, usually through command-line utilities and manual editing of configuration files. This also requires users to have knowledge on how to make a system bootable. Rebuilding a system using a disk image backup requires experienced Linux administrators and could take days, weeks or longer resulting in crippling downtime for an organization.

Advances in File-based Backup
File-based backup tools today can automate the process of recording every aspect of a system separately such as disk, filesystem and boot loader configuration while supporting all popular Linux storage configuration tools (i.e. LVM and Software RAID). This detailed backup information is used to greatly simplify the recovery of a failed system from scratch, even if hardware differences are detected on the new system. Furthermore, systems rebuilt from the ground up using file-based backups often times operate better than the original because there is virtually no fragmentation when the restore is completed.

Flexible recovery based on file-based backup
File-based backup products have the ability to reconfigure disks, partitions, filesystems and other storage solutions to fit onto new hardware. This ability to adapt a backup to fit new hardware or alter the system's storage configuration is called "Adaptable System Recovery" or ASR. Only backup solutions that gather details about the original system have enough information and flexibility to make the ASR process of altering configuration so simple even novice Linux administrators can quickly perform the recovery. Once new configuration is completed, data files from the backup are easily restored onto the new hardware. Finally, the system is made bootable based on the new hardware.

The revolutionary adaptability of ASR found in file-based backup tools creates further added value for system administrators because these products can now be used for far more than just reactive tasks such as disaster recovery.

Applications for ASR:
Reactive

• Disaster Recovery- restore systems in minutes after a crash, even if hardware is not the same as the original

Proactive

• Provisioning/cloning- a single backup "golden image" can be used to provision different systems, even if disks, adapters or other elements are not the same.
• Storage software migration- change configuration on the same system for improved performance and availability
• Hardware migration- install the same system onto newer or virtual systems

New system backup management features
Products using file-based system backup have not neglected to consider a system administrator's daily backup responsibilities. These products now incorporate functionality for backup management as well as some of the most advanced features seen in backup and recovery solutions for Linux and AIX. Some advanced features designed to simplify daily backup management for system administrators include:

• Graphical, Web and Command line interfaces
• Local and remote backups to disk or tape devices
• Sequential and random tape autoloader support
• Support for SAN storage solutions
• Tivoli Storage Manager integration
• Oracle database backup support
• Backup data encryption
• Multiple compression levels

File-based Backup Solutions Provide Most Bang for the Buck
Inexpensive products exist that combine both file-based backup management and ASR in one program. Look for a file-based system backup product with advanced features like those mentioned above. In turn, regular backup responsibilities such as automatically verifying backups and encrypting backup data will become much easier. Additionally, combined ASR capabilities greatly reduce downtime and required expertise for both reactive (even bare metal) and proactive recovery projects. File-based system backup and recovery solutions are an economical and more comprehensive option than their image-based counterparts.

About the Author
Anne Stobaugh is an independent contractor working with Storix Software to educate Linux and AIX users on the advantages of file-based backup and recovery solutions.
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