Choosing the ideal storage solution is critical for your data center. SAS (Serial Attached SCSI) SSDs and SATA (Serial ATA) SSDs are both excellent options for businesses with higher storage requirements but deciding between the two SSDs can be a challenge.
How do SAS and SATA compare in terms of performance?
SSD data transfer speeds vary based on a drive’s bus interface, which is the communication system used to transfer data back and forth with the host. SAS and SATA are two different bus interfaces.
SAS vs SATA interfaces:
- SAS: Serial Attached SCSI (Small Computer System Interface)
- SATA: Serial ATA (Advanced Technology Attachment)
SAS utilizes an upgraded version of SCSI, a robust technology limited by its use of parallel communication. Although more data is sent at once with parallel communication, it takes longer to synchronize the data, effectively slowing down the data rate. In contrast, serial communication is much more efficient with less data sent at once, minimizing synchronization time and signal interference.
SAS carries over the reliability of SCSI but just as importantly, converts the connection from parallel to serial. Likewise, SATA utilizes a serial version of ATA, which is an interface with the controller integrated on the drive. SAS and SATA SSDs offer superior data transfer over their outdated, parallel counterparts.
Half-Duplex vs Full-Duplex Transmission
This is where SAS and SATA start to diverge greatly in terms of performance. A key difference between the two is that SATA uses half-duplex transmission while SAS uses full-duplex transmission.
- Half-duplex: one direction information transfer at a time
- Full-duplex: two direction information transfer at a time
So what exactly does this mean? Half-duplex is like a one-lane road. It only allows cars to drive in one direction at a time. Full-duplex is more like a two-lane road. It allows different cars to drive in either direction at the same time. Two-lane roads allow for more cars (data) to drive through at any given time compared to one-lane roads, so traffic (data transfer) is more efficient.
Because SAS utilizes a full-duplex design, it can transfer data quicker than SATA, with transfer speeds upwards of 12Gb/s. When it comes to pure speed, SAS wins hands down.
What about drive endurance?
One of the key metrics in evaluating the durability of hard drives is MTBF (Mean Time Before Failure):
- MTBF rating for SAS SSDs: ~2 million hours
- MTBF rating for standard SATA SSDs: ~700,000 hours
SATA SSDs may have lower durability ratings but are generally more cost friendly than SAS drives. As mentioned in our SSD article
, there is also a tradeoff between endurance levels and storage capacities, which means that SATA drives offer higher capacity sizes at lower prices. For networks with modest levels of traffic and infrequent usage, SATA may be a better fit with less of an emphasis on durability and more on affordability.
In enterprise computing, there is a much higher emphasis on durability. Enterprise computing involves repeated usage from a high-traffic, large network of users which elevates the durability requirements for storage drives. SAS SSDs are designed to withstand the wear and tear from constant read/write while delivering consistent performance. With higher MTBF ratings, SAS drives are essential for handling enterprise-level traffic. SAS drives also provide a dual-port configuration to back up data if necessary.
How do they compare for data integrity?
The tolerable margin of error for enterprise-grade computing is much lower than consumer-grade computing. SATA has some general data protection mechanisms, but advanced data protection is a defining feature on SAS drives.
- Built-in advanced ECC (Error Correction Code) algorithms
- SCSI programming to pinpoint errors
These features allow for a lower UBER (Uncorrected Bit Error Rate). Low error rates are ideal for virtualization or building a RAID (Redundant Array of Independent Disks) to back up data on virtual drives. More advanced ECC algorithms also strengthen encryption on the drives. SAS drives are built for end-to-end data protection, giving SAS a clear advantage over SATA in this regard.
So which SSD is right for my data center?
Choosing between SAS or SATA really hinges on what kind of data center you are trying to run. The general notion is that SATA drives significantly outperform HDDs but lack many of the essential features for full-scale enterprise computing and are reasonably priced as such.
On the other hand, SAS drives are in a class of their own for enterprise computing with faster read/write performance, higher endurance for high-traffic usage and extra data protection ideal for virtualization. SAS ports can also be modified to support SATA drives. In recent years, M.2 NVMe (Non-Volatile Memory Express) SSDs have gained traction but their hefty price tag makes them more of a luxury for enterprise computing when matched up against SAS or SATA.
If you are simply looking for faster storage performance at competitive price points, SATA is a great option. If enterprise computing is a cornerstone of your business, SAS is your best bet. Axiom offers both SAS and SATA SSDs in a wide range of storage capacities and compact form factors. Axiom SAS and SATA drives are hot-swappable and include OEM caddies for easier and more efficient installation.