SAS vs. SATA - A Primer and Backplane Server Guide – TechMikeNY

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SAS vs. SATA. A Primer and Backplane Compatibility for Enterprise Servers

 

If you are new to the world of servers, a term that you may be hearing is “SAS” (Serial-Attached SCSI).  While the majority of desktops use SATA (or Serial ATA) hard drive connectors, SAS is an Enterprise-class hard drive connector that allows for greater reliability and faster data transfer speeds.  In this post, we’ll cover the key differences between SATA vs. SAS, considerations you want to make in regards to which is best for your server, as well as any compatibility concerns with server backplanes. 

SAS vs. SATA.  The Basics. 

In a nutshell, SAS drives are more reliable than SATA, having a lower Mean Time Between Failure (MTBF), while also having faster data transfer speeds than SATA drives.  The higher rate is achieved through the “full-duplex” functionality of SAS – the ability to send and receive data at full speed concurrently (SATA drives can only send or receive data at one time).  

It is for these reasons that SAS drives are mainly designed for Enterprise servers. Those devices are expected to handle a lot of data with a very high level of reliability for several end users. 

There are other differences between SAS and SATA; if you want to deep-dive into the full technical specifications, Intel provides this helpful server guide comparison chart.

What is the physical difference between the ports?

At first blush, SAS and SATA ports look very similar – they both use fifteen-pin power and seven-pin data connections.  The key way to tell the difference between the two is SATA drive will have a split between the data and power, whereas the SAS connector will have more of a single edge. 

The above image shows a side-by-side comparison of a SAS and SATA drive. The SAS port has a bar that prevents a SATA cable from plugging into it.

Here is another visual comparison of the two drive ports - SAS on the top; SATA on the bottom.   Note the spacing between the power and data connections on the SATA drive.

Due to their physical similarities, there are some cross-compatibility features between SAS and SATA (more on that below). 

Which is better for me?

Since SAS is designed with reliability and concurrent data in both directions, it is more frequently installed in large-scale data center servers.  That said, any server which is hosting a large number of end-users online, or where speed is a premium, would benefit from SAS drives. 

Here are some additional considerations with SAS and SATA drives:

  • Price.  SAS drives will cost approximately 10% more than a SATA drive of the same volume as of this writing. 
  • Backplane Compatibility. Virtually all Enterprise-class servers – of which TechMikeNY primarily sells – have backplanes that can take either SAS or SATA drives. 
  • RAID considerations. While these servers can take either drive, you CANNOT have a SAS and SATA drive in the same RAID 
  • Mixing SAS and SATA in a server. While you cannot have different drives in the same virtual disk environment, you can have SAS and SATA drives housed in the same server.  (A frequent configuration is to run your OS off of a SAS drive for speed and then utilize several SATA drives for a storage configuration.)

If you ever have any questions on what hard drives are best for your configuration and server build, never hesitate to reach out to us at info@techmikeny.com!

 

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