Authors: Franco Castaldini, Sr. Product Marketing Mgr. and Kent Bransford, Sr. Technical Editor,
Seagate Technology
As the pace of Serial Attached SCSI (SAS) product introductions continues to accelerate, IT managers enjoy an increasingly broad range of SAS storage solutions from which to choose. While the inherent performance advantages of SAS disk drives are certainly compelling, savvy IT professionals are even more excited about the revolutionary role SAS will play in the larger context of storage infrastructures.
Storage is entering a new era of cost-effectiveness and efficiency, driven by the growing movement towards specialized storage solutions. The value proposition of such storage is straightforward: Optimize price/performance by matching the storage device to the specific characteristics of the data and/or storage environment. SAS is a fundamental enabling technology in this specialization revolution, seamlessly integrating multiple types of storage devices in one enterprise-class infrastructure.
Seagate maximizes the value of every SAS deployment by delivering a comprehensive range of disk drives purpose-built to leverage the full gamut of SAS strengths (superior throughput, compatibility with SATA, enormous scalability). Seagate’s holistic approach enables enterprises to simply and cost-effectively meet all of their storage needs (online and nearline applications, high-density storage) with a single SAS infrastructure.
Seagate: Beyond the 10K Compromise
Over the years, 3.5-inch 10K-RPM disk drives have performed admirably in a wide variety of storage applications. But now these generalized, “jack of all trades” drives are being supplanted by more specialized, application-specific devices. As shown below, 10K SAS drives are a costly compromise, out of place in today’s more efficiency-focused SAS storage environments:
- Online:
Eclipsed in throughput and price/performance by Seagate Cheetah 15K.4 drives - Nearline:
Soundly trounced in cost/GB by nearline-ready Seagate NL35 SATA drives - High-Density:
Outclassed in IOPS/U by new Seagate Savvio 2.5-inch enterprise drives
Online Storage: Seagate Cheetah® 15K.4
The advanced architecture of SAS (point-to-point connectivity, full duplex operation, dual ports) eliminates the significant performance bottleneck imposed by parallel SCSI’s shared-bus topology. So it makes little sense to effectively reintroduce a performance bottleneck by using slower SAS drives.
Cheetah 15K-RPM drives not only deliver faster throughput, they also free up enclosure space for more nearline drives. For example, a 2U (12 bay) enclosure/rack space filled with five Cheetah 15K.4 drives (online duty) and seven NL35 SATA drives (nearline duty) provides 11% more online performance (IOPS) and 17% more nearline capacity than the same enclosure/rack space filled with six 10K SAS drives and six NL35 SATA drives.*
Simply put, Seagate Cheetah 15K.4 SAS disk drives are purpose-built to address the performance deficiencies of 3.5-inch 10K SAS drives, and in so doing enable greater cost-effectiveness in SAS deployments. Requiring fewer drives to provide equal or better performance, Cheetah 15K.4 drives deliver lower TCO by ensuring:
- Less supporting infrastructure
- More enclosure/rack space for nearline storage
- Lower maintenance and storage-management costs
- Greater reliability due to fewer potential points of failure
- Higher IOPS/U
Nearline Storage: Seagate NL35 SATA
Nearline applications entail large quantities of data that does not justify the cost of high-availability, online storage, but must still be readily accessible at a moments notice. While nearline data activity is far less frequent than online activity, both involve random reads/writes that force drive heads to rapidly and repeatedly traverse a drive’s disks.
Seagate NL35 SATA drives are purpose-built to deliver the nearline-class reliability standard of 1.0 million hours MTBF while withstanding the rigors of random reads/writes and 24/7, always-on operation. In contrast, the typical 600,000 hours MTBF rating of desktop-class SATA drives is obtained in the mild environment of sequential reads/writes and 8/5 power-on hours, and thus has no relevance to nearline duty.
While 10K SAS drives theoretically offer greater performance than nearline-ready NL35 SATA drives, in actual nearline applications this advantage is largely academic. More importantly, 10K SAS drives are vastly more expensive in terms of capacity, with cost/GB roughly four times higher than NL35 SATA drives.
High-Density Storage: Seagate Savvio™
Seagate Savvio 2.5-inch 10K SAS disk drives are uniquely suited to meet the dual objectives of performance and space efficiency. These compact drives are 70 percent smaller than 3.5-inch 10K SAS units, enabling them to deliver 130 to 150 percent greater system performance in the same footprint (IOPS/U) and boost data center ROI. To look at it another way, 2U storage arrays equipped with Savvio SAS drives provide:
- 70 percent more IOPS (2U box vs. 3U box)
- 33 percent reduction in rack space (2U vs. 3U)
- 155 percent more IOPS (on IOPS/U basis compared to 3U)
Savvio drives use 40-50 percent less power than 3.5-inch drives and thus run cooler and require less airflow, enabling greater storage density and data center space efficiency. Savvio drives can also significantly expand the role 1U servers and blade servers play in the enterprise. For example, 1U servers equipped with six Savvio drives can deliver full RAID 5 functionality, outperforming 2U servers by 150 percent while using half the space.
Conclusion
Seagate is leading the storage specialization revolution with purpose-built disk drives that fully exploit the broad capabilities of SAS. Compatibility with SATA enables a single SAS-based subsystem carrying Seagate Cheetah 15K.4 SAS drives and nearline-ready Seagate NL35 SATA drives to efficiently meet both online and nearline needs. And SAS is an optimal complement to Seagate Savvio drives, its exceptional scalability easily handling the greater drive counts found in high-density storage solutions.
Such complementary relationships between infrastructure and storage device are key to maximizing the cost-effectiveness of any storage solution. Seagate has specifically engineered a family of SAS-based disk drives that leverage the strengths of SAS to deliver optimal storage performance and value.
*All online drives 146GB, all nearline drives 400GB. Test results from IBM xSeries 336 with EXP 400, general transactional workload, RAID 5.
