Книга: Windows Server 2012 R2 Storage, Security, & Networking Pocket Consultant

Common backup solutions

Common backup solutions

Capacity, reliability, extensibility, speed, and cost are the issues driving your backup plan. If you understand how these issues affect your organization, you’ll be on track to select an appropriate backup solution. Some of the most commonly used backup solutions include the following:

? Tape drives Tape drives are the most common backup devices. Tape drives use magnetic tape cartridges to store data. Magnetic tapes are relatively inexpensive but aren’t highly reliable. Tapes can break or stretch. They can also lose information over time. The average capacity of tape cartridges ranges from 24 gigabytes (GB) to 160 GB. Compared with other backup solutions, tape drives are slow. Still, the selling point is the low cost.

? Digital audio tape (DAT) drives DAT drives are quickly replacing standard tape drives as the preferred backup devices. Many DAT formats are available. The most commonly used formats are Digital Linear Tape (DLT) and Super DLT (SDLT). With SDLT 320 and 600, tapes have a capacity of either 160 GB or 300 GB uncompressed (320 GB or 600 GB compressed). Large organizations might want to look at Linear Tape Open (LTO) tape technologies. LTO-3, LTO-4, and LTO-5 tapes have uncompressed capacity of 400 GB, 800 GB, and 1500 GB, respectively (and compressed capacity of twice that).

? Autoloader tape systems Autoloader tape systems use a magazine of tapes to create extended backup volumes capable of meeting an enterprise’s high-capacity needs. With an autoloader system, tapes within the magazine are automatically changed as necessary during the backup or recovery process. Most autoloader tape systems use DAT tapes formatted for DLT, SDLT, or LTO. Typical DLT drives can record up to 45 GB per hour, and you can improve that speed by purchasing a tape library system with multiple drives. In this way, you can record on multiple tapes simultaneously. In contrast, most SDLT and LTO drives record over 100 GB per hour, and by using multiple drives in a system you can record hundreds of GB per hour. An example enterprise solution uses 16 LTO drives to achieve data-transfer rates of more than 13.8 terabytes (TB) per hour and can store up to 500 tapes, for a total storage capacity of more than 800 TB.

? Disk drives Disk drives provide one of the fastest ways to back up and restore files. With disk drives, you can often accomplish in minutes what takes a tape drive hours. When business needs mandate a speedy recovery, nothing beats a disk drive. The drawback to disk drives is a relatively high cost compared to tapes (though you’d also need to compare the initial hardware investment).

? Disk-based backup systems Disk-based backup systems provide complete backup and restore solutions by using large arrays of disks to achieve high performance. High reliability can be achieved when you use redundant array of independent disks (RAID) to build in redundancy and fault tolerance. Typical disk-based backup systems use virtual library technology so that Windows perceives them as autoloader tape library systems, which makes them easier to work with. An example enterprise solution has 128 virtual drives and 16 virtual libraries per node for total storage of up to 7.5 TB per node. When fully scaled, this enterprise solution can store up to 640 TB and transfer up to 17.2 TB per hour.

NOTE Disks and disk-based backup systems can be used between the servers you are backing up and an enterprise autoloader. Servers are backed up to disk first (because this is very fast compared to tape) and later backed up to an enterprise autoloader. having data on tapes also makes it easier to rotate backup sets to off-site storage. That said, tape backups are increasingly being replaced with disk backups. If you back up to disk arrays, you can move data off site by replicating the data to a secondary array at an alternative data center and that data center can be in your private cloud or a third-party service’s cloud.

Before you can use a backup device, you must install it. When you install backup devices other than standard tape and DAT drives, you need to tell the operating system about the controller card and drivers that the backup device uses.

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