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|When to use SATA|
- NL35 (Seagate Technology Inc.). Seagate's NL35 drive family is a high-capacity, hybrid drive design that
comes in two flavors: a single-ported SATA interface and a dual-ported FC interface. The NL35 family overcomes the limitations of SATA, such as port redundancy, but has a number of drawbacks. For example, the NL35 is a niche drive technology developed by a single disk drive manufacturer, Seagate, for Hewlett-Packard Co. The NL35 is also very pricey vs. other SATA drives; a 250GB SATA drive is approximately $262, while an NL35 drive with an FC interface and equivalent capacity is $695.
Standard SATA, coupled with low-cost, chip-based FC-SATA bridging technology, is another way to kick SATA up to the enterprise-class level. The bridging technology allows SATA drives to emulate FC drives, and to plug seamlessly into FC-based storage systems consisting of FC controllers and FC-AL loops to the JBOD. This configuration dual ports the SATA drives and delivers end-to-end redundant data paths.
By distinguishing and translating between user sectors (520 bytes) and media sectors (512 bytes), bridging technology lets SATA drives exhibit the data integrity features of performance-optimized FC drives. Bridging chips can also improve the fault tolerance of SATA drives by providing drive diagnostics and failure identification.
The combination of SATA and low-cost, chip-based bridging technology has significant merit. It addresses the inherent technology limitations of the standard SATA interface and makes SATA technology applicable for a variety of primary and secondary storage apps. Moreover, it protects enterprise investments in FC platforms and provides a seamless path for the introduction of SATA without massive capital outlays and forklift upgrades. Finally, because the technology emulates FC using SATA drives from any vendor, it delivers significant flexibility.
|A sampling of SATA products|
For secondary storage, SATA drives are ideal repositories for disk-based backups and online archives. In each case, users must grapple with massive data sets on the order of petabytes and data growth at or above 100% per year. Disk media performance, though not negligible, isn't as critical as it would be in many production application environments.
Data for critical applications, particularly those sensitive to I/O latency, is best stored on performance-optimized SCSI or FC drives. For other categories of application data that are business- rather than mission-critical and aren't performance-sensitive, SATA with enterprise-class extensions is a natural fit. Examples of these applications may include data mining/warehousing, unstructured content repositories, e-mail in certain environments and aged mission-critical data.
Because the cost advantages of SATA are huge compared to FC drives, a storage admin may be tempted to deploy SATA in environments where the technology may not yet be appropriate. Look for solutions, albeit more costly than plain SATA, that add an extra measure of reliability and protection. Companies should favor SATA solutions that incorporate low-cost, chip-based bridging technologies and preserve existing investments and expertise with FC-based products. While chip-based bridging technology narrows the price gap between SATA and FC drives, the improvements in reliability, performance and data integrity put all of the pieces in place for successful enterprise SATA deployments.
This was first published in April 2005