Which is better - SAS or SATA Drives in Servers?
If you have a server, it needs storage drives. Whether you are using hard drives, solid-state drives, NVMe drives, or another storage medium, those drives need the ability to communicate with the rest of the system.
For that communication, you have a multitude of connection types. When it comes to server systems, the two most prominent connections are SAS and SATA. Which is better for your server? That depends on how you intend to use it. We can take a closer look at SAS and SATA to see when one might outperform the other.
What Is SAS?
SAS stands for serial attached SCSI (yes, an acronym within an acronym). SCSI stands for Small Computer Systems Interface. Terminology aside, SAS is a connection used for communication between motherboards and storage drives. In modern systems, it’s most likely used to connect a hard drive or solid-state drive to the rest of the computer system.
SAS is designed specifically to improve diversity in connectivity and configurations. It uses four wires to communicate, but those wires are separated into two different cables. Despite that separation, it is not a parallel design. Each cable has incoming and outgoing wires. This separation allows each SAS drive to hook up in different ways, leading to longer, multi-device serial connections.
Advantages of SAS
When comparing SAS to SATA, there are a few clear advantages. First, the average read/write speed for SAS is higher. This mostly comes from faster read speeds on SAS designs. Because it’s faster at reading, SAS systems are better for storage that is called up very frequently — such as in a server.
The split-cable connection also makes SAS better in RAID and other robust configurations. SAS also has an easier time linking additional drives, making the maximum storage potential higher.
Disadvantages of SAS
Despite that potential, a single SAS drive usually holds less data than a single SATA drive. This means you need to buy more hardware to match the same storage capacity. On top of that, SAS tends to cost more per unit than SATA, compounding the expense.
Generally speaking, SAS is only worth this cost if the system needs multiple storage drives anyway. In such systems, the improved read speed and connectivity can justify the higher cost.
What Is SATA?
SATA stands for Serial Advanced Technology Attachment. This is a connection type that has been around for decades, and it was long the standard for connecting desktop and laptop storage devices. These days, that standard is trending in the direction of PCIe connections, but SATA is still used in countless systems around the world.
SATA utilizes a one-cable connection that has four separate wires. Two conductors are designated for sending data while the other two retrieve data. This makes it a serial connection (as opposed to a parallel connection). Additionally, there are ground cables between the conductors that lessen interference and ultimately improve performance.
In addition to the communication cable, SATA arrangements include a separate power cable that runs the storage device.
Pros of SATA Drives
SATA has a faster pure write speed than SAS. Even though SAS has the higher average for read and write, the faster write speed of a SATA cable provides advantages in specific cases. If the computer system does not need to continuously call up data, higher write speeds are worth the trade-off in read speeds.
SATA drives also have higher per-device storage capacity. Even with more storage, they cost less on average than SAS drives.
Cons of SATA Drives
The major drawback to SATA design is the limitation on configuration. Using SATA is much less efficient for redundant storage setups (like RAID). SATA also struggles with continuous read operations, making it less popular in server systems.
When comparing SATA and SAS, there are clear pros and cons for each case. When it comes specifically to server designs, SAS is more popular because those setups typically use multiple storage drives anyway. Some specific server setups might prefer SATA (if the server doesn’t utilize multiple drives), but in general, SAS is the preferred choice for a server.
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