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ストレージ 3Ware TwinStorのPDF インフォメーションシートをオンラインで閲覧またはダウンロードできます。3Ware TwinStor 10 ページ。 A compelling case for multiple drives in pcs, servers and workstations

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The solution that accomplishes this is 3ware'sTwinStor technology, which simultaneously provides the fault tolerance of disk

mirroring (RAID 1) and the read performance of striping (RAID 0) with superior transaction rates. By using a TwinStor-

enabled ATA RAID controller [1], such as 3ware's Escalade 7000, along with low-cost ATA drives, a compelling case can be

made for multiple drives per PC.

This white paper discusses trends in data backup strategies and compares the associated costs with the approach offered

by TwinStor technology. It also goes under the hood of the technology and uncovers many of the groundbreaking

techniques. Within the descriptions of the design concepts, brief tutorials of RAID architecture and disk drive hardware

components, offer insights into how TwinStor's algorithms are able to achieve such striking performance gains.

Having laid this groundwork, the discussion concludes with performance and cost comparisons with SCSI that further

highlight the benefits of the TwinStor technology. It becomes clear that there are many applications and markets that can

effectively make use of TwinStor to prevent data loss and increase storage system efficiency.

Total cost of ownership

The economic justification for mirroring is based on the cost of the second drive compared to the backup and recovery costs

after a drive failure. Depending on the business environment, backups can be done several different ways.

Corporate desktop PCs and small servers are often backed up automatically over a network. The total cost of this backup

strategy can be quite high when all costs (hardware and software, increased network capacity and system administrators'

time) are included. A large corporation recently spent over $1000 per PC for a centralized hierarchical backup system. Disk

mirroring would have solved the daily backup problem at a much lower cost.

Small businesses typically rely on manual backups to tape or other removable media. Total cost of ownership includes risk of

losing everything if a backup was not done recently. Even when backups have been done properly, a drive failure may cause

any business to close – requiring down time-to repair the hardware, reload the operating system and applications and

restore the data.

Many home PCs and non-critical business PCs do not adhere to any regular backup procedure, even though the effort to

recover from a disk failure could be significant. For these users, the increased performance combined with the added fault

tolerance may be a compelling reason to spend a modest amount for a second drive.

Protecting data in this fashion is one of the initial philosophies that spawned RAID technology.

Background of RAID

Mirrored disks have been common in the industry for many years. Disk mirroring, also called shadow sets or RAID 1, uses a

pair of disks with the identical data. Every write is sent to both drives to maintain identical copies at all times. Disk mirroring

is used in many commercial systems and has been the subject of academic research at the University of California at

Berkeley [2] and elsewhere.