Backup Devices
There are several types of backup systems for needs ranging from backing up the hard disk on a personal computer to backing up large amounts of information for archiving and disaster recovery.
What is tape backup?
Tape backup is the process of copying data
to a tape cartridge device. This process protects your data in the event of a hard disk crash or comparable failure. You can choose to manually
or automatically run tape backup.
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What to remember about tape backup
- Tape backup takes data from the computer or network and stores it on tape media.
- Tape backup helps prevent data loss from disasters.
- Tape backup can be used for large or small computer systems.
- Tape backup provides a means to safeguard data offsite.
Why tape backup
- Reliability - Tape drives rarely crash and are considered a much safer place to store data than hard drives. Tape drives validate the data as it is written, ensuring the data is really being backed up.
- Low cost - The price per gigabyte of storage space is relatively low compared to other technologies.
- Rugged and removable - Media can be removed and stored in a safe place (a fireproof vault or offsite location) to be used later in the event of a catastrophe in the data center.
- Rewritable - All tape media can be written over, with the exception of WORM technology (write once read many). WORM technology is typically used in the finance industry and other industries where an accurate and unalterable audit trail is required.
Limitations of Tape Backup
- Slower write speed
- Slower read speed
- Slower access time (you have to load the tape and locate the data on it)
Types of Tape Devices
- Tape Drive - A standalone device that connects to a server. There are three primary types of tape drives: internal, external and rack-mount (usually holds two drives).
- Tape Autoloader - Generally used in a multi-server environment or when a backup requires multiple tapes. Tape autoloaders use robotics to automate backup and provide unattended backup. Autoloaders have one tape drive and range from 7-12 tape slots.
- Tape Library - All the features of an autoloader with increased capacities for tape drives and tape slots. A good tape library is scalable to multiple tape drives and tape slots. A typical small tape library has one or two drives and 20-40 tape slots, while a large tape library may be configured with 12 tape drives and hundreds of tape slots. Multiple drives speed up the backup process when there is a large backup and it is becoming difficult to meet the backup window.
Tape Formats
Over the years several tape formats have been made available. But, a few have emerged as the dominant formats. These formats are: Linear Tape Open (LTO), Digital Linear Tape (DLT), Digital Audio Tape (DAT) and Digital Data Storage (DDS).
Linear Tape Open (LTO) is an industry leader because of its open format. It also offers large storage capacity and provides the fastest speeds per capacity. According to an IDC research report published in May 2006, LTO-based tape drives attained an 82.4 percent unit shipment share in the midrange tape drive ("Worldwide Tape Drive 2006-2010 Forecast and Analysis" by Robert Amatruda (IDC #201542).
- High capacity - Allows for up to 400GB native/800GB compressed capacity in a single compact cartridge. The cartridge is smaller than existing single-reel tape cartridges.
- High data rate - Data transfer rates of 80-160MB/ second (2:1 compression) for the third generation of the 8-channel version.
- LTO-CM (Cartridge Memory) - Provides a redundant file log as well as user-defined information. Immediate access to information is available through an external reader so it is not necessary to insert the cartridge
into a drive.
- Multi-sourcing - Multiple sources for media and drives ensure investment protection.
- Compliance testing - Testing by an independent organization promotes compliance to the specification. This ensures you will experience consistent performance.
Digital Linear Tape (DLT) is the second most common tape format and offers 800GB native/1.6TB compressed capacity. DLT uses linear serpentine recording with multiple tracks on half-inch (12.6 mm) wide tape. The cartridges contain a single reel and the tape is pulled out of the cartridge by means of a leader tape attached to the take-up reel inside the drive. The drive leader tape is buckled to the cartridge leader during the load process. Tape speed and tension are controlled electronically via the reel motors; there is no capstan. 4 to 6 rollers that touch only the backside of the tape guide the tape. Tape material is metal particle tape (MP/AMP.)
SDLT adds an optical servo system that reads servo patterns on the back of the tape, in order to keep the data tracks on the front of the tape correctly aligned with the read/write heads. This is important for newer tape media, which have very thin dense data tracks (256, 384 and 768 data tracks on a half-inch wide tape are now common).
All SDLT drives support hardware data compression to provide increased cartridge capacity. The often-used compression factor of 2:1 is optimistic and generally only achievable for text data. A more realistic factor across a file system is 1.3:1 to 1.5:1.
Manufacturers commonly guarantee media for 30 years of data retention under specified environmental conditions. However, keep in mind that media is easily damaged by mishandling (dropping or improper packaging during shipment).
Advanced Intelligent Tape (AIT) reflects 55 years of innovation and technical excellence in magnetic recording. AIT features helical-scan recording, unique Memory-in-Cassette (MIC) architecture, advanced read/write head technology and the exclusive use of Advanced Metal Evaporated (AME) media. These characteristics result in high capacity and performance, outstanding reliability, fast data search, and superior data protection through the use of Write-Once-Read-Many (WORM) capability.
- Capacity for all levels - AIT offers great value for a business just starting backups of 20GB all the way to a large-sized business that requires up to 6.4TB of native storage capacity. Having an AIT entry level tape backup solution allows DDS/DAT users to migrate into the AIT format with confidence knowing that AIT will match their growing needs without the need to switch formats in the near future. ADLC compression (2.6:1) allows AIT to support up to 16.64TB of storage capacity for businesses requiring high-capacity storage.
- Flexible connectivity - AIT internal drives are available in SCSI, ATAPI, SATA and USB interfaces.
- Advanced Metal Evaporated (AME) media - The media is characterized by an 8mm form factor in a compact 3.5-inch drive mechanism.
- R-MIC - A memory chip built into the data cartridge that stores a system log, search map and user-definable information allowing fast data searches.
- High reliability - MTBF of 400,000 hours at 100% duty cycle / Media uses 30,000 end-to-end passes
- Write Once, Read Many (WORM) functionality - Added level of data protection. WORM-enabled tape drives and media cartridges allow backed up data to be accessed but not over-written, altered or erased, offering an extremely cost-effective storage technology for storing sensitive and regulated archive data.
Digital Audio Tape (DAT/DDS) format was originally designed for audio use, but through the ISO Digital Data Storage standard it has been adopted for general data storage. It stores from 1.3GB to 72GB on a 60- to 170-meter tape depending on the standard and compression. It is naturally, sequential-access media and is commonly used for backups. Due to the higher requirements for capacity and integrity in data backups, a computer-grade DAT was introduced, called DDS (Digital Data Storage).
Backup Systems
Data backups can take several hours to complete, and they are commonly done during off-peak hours to minimize the impact on business operations. Once a backup is complete, recovering data later can be a time-consuming process. Since time is critical in a fast-paced business environment, IT professionals are always looking for ways to reduce backup windows and make data recovery more efficient.
IT professionals are now finding that disk-based storage is a viable alternative to traditional backup systems. Here are some of the advantages of disk-based storage:
- Faster backups than tape-based systems
- Faster data recovery times than tape-based systems
- Cost competitive with tape systems
- RAID capabilities help maintain data integrity
Disk backup systems can be implemented in several different ways:
- Pack your backup server with large capacity hard drives
- Backup to a disk array such as a SAN
- Backup to a disk-2-disk appliance
- NAS appliances, while this use to be popular some of the inherent problems like disk fragmentation have made it a less popular option today
Disk or Tape
Tape is an inexpensive solution for offline data storage, but it does have drawbacks. The slow transfer speeds result in lengthy backup windows and the media itself is problematic. Once stored on the tapes, data can be difficult to locate. The tracking and storage of tapes can be costly. And tapes are subject to loss, theft and damage.
Many organizations choose disk-based storage such as SATA or SAS disk arrays over tape solutions because it offers superior performance and streamlines data recovery. Another important advantage is that disk-based storage offers RAID capabilities to help ensure data integrity.
In addition to performance, backup times and recovery features, total cost of ownership should be considered when comparing disk and tape solutions. While some solutions may appear to be more expensive than others, the total cost of ownership may be lower.
Virtual Tape Libraries
For a company that has made a large investment in a tape system and doesn't want a completely new storage architecture, a virtual tape library (VTL) is a convenient solution. A VTL is a hard-disk storage system that appears as a traditional tape system to backup software and hierarchal storage management (HSM) tools. A VTL offers increased performance over a true tape system.
A VTL working with management software enables IT administrators to move nonessential information from hard disk storage to tape storage. This type of system also helps IT administrators who need to balance data archiving and storage performance. A VTL provides fast data access while giving IT administrators the ability to do complete tape backups without network interruption.
Emerging Backup Technology
As with any area of technology, data backup solutions change and improve over time. Here are some examples of emerging technology.
- Content-addressed storage (CAS) - Disk arrays are being used for single-instance storage or CAS. It is referred to as single-instance storage because CAS stores only one copy of a file - even when multiple copies are being backed up. CAS also includes fingerprinting technologies that ensure the integrity of files.
- Continuous data protection (CDP) - Disks are using "snapshot" and CDP techniques to speed up recovery times and prevent data loss. These periodic saves of system data make it possible to recover a system with virtually no data loss.
- Data deduplication - Similar to CAS, deduplication is single-instance storage. Only one copy of a file is saved to disk media. By eliminating duplicate files, storage requirements will be reduced and storage costs will also decline.
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