Nearline SAS and Enterprise SATA:
Summary for Nearline SAS
- Tier-2 Dollar per Gigabyte Advantage of SATA
- Up to 30% performance improvement over similar SATA 7200 RPM drives
- Dual port without an interposer means less interconnects
- Available in PowerEdge servers and PowerVault enclosures
Dell's Nearline SAS, available in PowerEdge servers and PowerVault enclosures, is an enterprise hard drive combining the head, media, and rotational speed of traditional enterprise class SATA drives with the fully capable SAS interface typical of 10K/15K RPM SAS drives. These features provide a clear edge over Enterprise SATA drives.
While SAS 10K and 15K RPM on-line hard drives are primarily used for applications considered mission critical and needing data readily available, nearline refers to data that is one-step removed from the fastest-access on-line data but still critical to business operations. Nearline SAS and Enterprise SATA together represent the Tier 2 classification of hard drive storage.
Enterprise SATA and Nearline SAS drives both offer the dollar-per-gigabyte advantage of tier-2 storage. Nearline SAS has advantages over SATA in terms of connectivity and performance. External storage environments cannot easily utilize SATA drives due to the signal integrity issues associated with SATA drives as they are placed farther and farther away from the nearest interconnect. To address the signal integrity issues, often an interposer is included. In addition to addressing the signal integrity issues, most interposers also add in the functionality of an additional port, or connection to the drive, for failover purposes. Nearline SAS drives already have the signal integrity required for external storage along with dual ports capable of full-duplex operation (where supported by the controller). Because Nearline SAS already has these features natively, it allows the elimination of the additional interconnect of the interposer.
Where host based server storage is the application, Nearline SAS still offers benefits over Enterprise SATA. Nearline SAS has the processing power typically found on higher-end tier-1 10K & 15K RPM SAS drives. This processing power combined with the efficiencies of SAS around queuing technology, allows for up to a 30% improvement in performance for Nearline SAS drives when operating in random IO environments.
Summary for Enterprise SATA
Dell's Enterprise SATA solution, found in PowerEdge servers and PowerVault enclosures, is a SATA interface for hard drives featuring specific design and manufacturing processes enabling 24x7x365 operations and 1.2 million hours MTBF within an enterprise environment.
- Best Dollar per Gigabyte Advantage within Enterprise class hard drives
- Rated for 24-hour by 7-days-a-week, 365 days a year operation
- Enterprise SATA 3.5" MTBF at 1.2 Million hours versus Consumer 3.5" SATA at 550K hours MTBF
Why Enterprise SATA over Consumer SATA
Enterprise SATA drives offer similar dollar-per-gigabyte advantages as Consumer SATA for tier-2 storage while also providing key design and process enhancements to allow for successful integration with specific Dell RAID controllers as part of Dell’s server and storage solutions. Typical SATA drives commonly found in the consumer, desktop and notebook arena lack the design and reliability characteristics required for the more strenuous enterprise environment. These consumer (or client) grade hard drives are typically rated at around 550K hours MTBF (Mean Time Between Failure) and not rated for 24X7X365 usage. While these Consumer grade drives are typically OK to utilize as boot devices, their capability to perform within the enterprise is limited. Enterprise SATA drives are designed with reliability and compatibility in mind. Enterprise SATA drives are rated for 24X7X365 operation, have Dell developed and certified firmware to ensure compatibility within Dell Servers and Storage, and also are typically equipped with Rotational Vibration circuitry to allow for the adjacencies of multiple drives, servers, and storage enclosures common within the enterprise.
Dell Update Package (DUP) support is now available on select Enterprise SATA hard drives. DUP allows for hard drive firmware to be updated without taking down the storage subsystem. Less downtime means higher productivity.