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SAS Hard Drives: Handy for Servers

HDD, SSD, SATA, SAS: With all the different hard drive technologies and terms, it can be difficult to see through the jargon and pick a SAS enterprise drive suitable for one's needs. A cut above your average SATA hard drive, SAS hard drives like Dell's offerings are enterprise solutions that can handle the pressure of constant use reliably. These drives are the standard type used in servers around the world.

What Are SAS Hard Drives?

SAS stands for Serial Attached SCSI, and refers to the interface between a server and a hard drive. The other interface users will encounter is the SATA interface, commonly used in consumer hard drives.

  • History: SAS is an evolution of the SCSI interface. The first SAS interface, SAS-1, had a bandwidth of 3 GB/s. The current version, SAS-3, handles 12 GB/s. The next iteration of the interface will support 24 GB/s. SAS devices have dual ports and use the SCSI command set.
  • Compared to SATA Drives: Physically, both drives look similar. However, SAS drives have additional features, such as error recovery, reservations, and block reclamation. In addition, they use higher signaling voltages, allowing them to use cables up to 10 yards long. SAS hard disk drives can have higher spindle speeds compared to SATA hard disk drives, reaching spindle speeds of up to 15,000 RPM. This translates to faster data transfer rates. In addition, SAS devices are tested and rated as more reliable drives. Lastly, they can also be larger in size, with some drives as large as 16 TB.

What Factors Are Important When Choosing a SAS Drive?

SAS is the internal hard drive interface of choice when it comes to servers such as Dell's PowerEdge servers. As these are mission-critical devices, the most important factors to consider differ from what one would look at when choosing a consumer drive.

  • Reliability: This is stated as the "availability" of an enterprise drive and is most often measured in mean time between failures (MTBF) or annualized failure rate (AFR).
  • Capacity: Large drives are useful for storing huge amounts of data that are not accessed very frequently. However, smaller drives with faster spindle speeds or those that use solid state technology are a better choice for faster data transfer rates. 
  • Type of Storage Medium: SAS drives may use traditional spinning hard drives or solid state drives as their storage method. SSDs are faster than the fastest HDDs and may be a good choice where speed is of the utmost importance.
  • Energy Saving: Servers are expected to run around the clock. Fitting them with drives that consume less power can result in significant power savings over time.

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