SAS vs SATA Hard Drives: What Is the Difference?

What is a SAS hard drive?

SAS stands for Serial Attached SCSI. The interface comes from the server world and is the serial successor to the older parallel SCSI. SAS drives sit in servers, storage systems and backplanes, the boards with bays for many drives. You will rarely find one in a regular desktop PC.

SATA (Serial ATA) is the interface in almost every PC, laptop and home NAS. Both interfaces are serial and use similar connectors. The difference lies in what they bring for always-on operation in large systems: 2 ports per drive, sending and receiving at the same time, higher transfer rates and extra data integrity checks.

One thing to keep in mind: the interface says nothing about the storage technology. A SAS device can be a hard drive with spinning platters or an SSD. This guide is about hard drives. SSDs with SAS or NVMe in the U.2 form factor are covered in our guide U.2 vs M.2.

What is the difference between SAS and SATA?

SAS transfers up to 12 Gb/s (SAS-3) or 22.5 Gb/s (24G SAS), SATA up to 6 Gb/s. SAS drives have 2 ports, send and receive at the same time and add data checks along the way. SATA drives have 1 port and are far more common.

The key differences at a glance:

The transfer rates of the SAS generations: SAS-1 at 3 Gb/s, SAS-2 at 6 Gb/s, SAS-3 at 12 Gb/s and SAS-4 at 22.5 Gb/s, marketed as "24G SAS". According to the SCSI Trade Association, 24G SAS doubles the effective bandwidth of 12 Gb/s SAS and stays backward compatible with 12 Gb/s and 6 Gb/s SAS. For a single hard drive, though, the interface is rarely the bottleneck: even the SAS version of an Exos 7E10 reads at most 236 MB/s according to its data sheet, which is about 1.9 Gb/s.

What does the data sheet say when the same drive comes in SAS and SATA?

Seagate builds the Exos 7E10 in both versions. According to the data sheet, SAS and SATA share the same spindle speed, the same cache, the same MTBF of 2 million hours and a 5 year warranty. The SAS version adds a 2nd port, 12 Gb/s, T10 DIF protection information and slightly faster reads.

The direct comparison of the 6 TB models from the Exos 7E10 data sheet:

The takeaway: the mechanics are the same, and so are the reliability figures on the data sheet. SAS adds the 2nd connection, the faster interface and T10 DIF (Data Integrity Field), a checksum that catches errors on the way between controller and drive. In return the SAS version draws a few tenths of a watt more on the data sheet. Seagate states the workload rating of 550 TB per year for the line as a whole.

What does dual port do on a SAS drive?

With dual port, a SAS drive is connected to the system over 2 paths. If a controller, a cable or a backplane fails, the drive stays reachable over the 2nd path. This is called multipath or dual domain and needs a system with 2 controllers or 2 backplanes.

In a home server with 1 controller the 2nd port does nothing, because there is no 2nd path. Dual port shows its strength in storage systems that must keep running when a part fails. The same goes for full duplex: SAS can send and receive at the same time. For a single drive, the everyday benefit is limited.

In an older overview for server boards with the Intel C602 chipset, Intel listed more differences: according to that table, a SAS drive typically gives up error recovery on a bad sector after 7 to 15 seconds, a SATA drive only after up to 30 seconds. Intel compared enterprise SAS with desktop SATA there and notes itself that the information may be dated. NAS drives with SATA bring their own RAID features too. Western Digital, for example, lists RAID error recovery control for the WD Red.

Can I connect a SAS drive to a SATA port?

No. SAS drives do not work on a plain SATA port or a SATA backplane. The other way round works: SATA drives run on most SAS controllers and SAS backplanes. The SCSI Trade Association states that SAS remains compatible with SATA.

To run a SAS drive you therefore need a SAS controller. That can be a controller on a server motherboard or a PCI Express add-in card, either a host bus adapter (HBA) or a RAID controller. Desktop motherboards usually only offer SATA and M.2. For the reverse direction, SATA drives on a SAS controller, SAS uses its own protocol for SATA devices, the SATA Tunneling Protocol (STP).

Here is how to check before you buy whether a SAS drive will work for you:

1. Check the controller: Does the manual of your server or motherboard list a SAS controller, or do you have a SAS add-in card? Plain SATA ports are not enough.
2. Check the backplane: Many servers have bays with their own board. The manual says whether it supports SAS or only SATA.
3. Match the generation: A 12 Gb/s SAS drive runs on a 6 Gb/s controller, at 6 Gb/s. According to the Exos data sheet, the SAS version supports 12, 6 and 3 Gb/s.
4. Plan the cables: You need the right SAS cable between controller and drive. The controller manual tells you which one.
5. Mind the sector format: Drives with 4Kn sectors need a controller and a system that support this format. What 512e and 4Kn mean is explained in our guide Seagate Exos vs IronWolf.

How much does a SAS hard drive cost right now?

The cheapest new SAS hard drive per TB on amazon.com right now is the Seagate Constellation ES.2 3 TB at $31.11 per TB (3 TB). For comparison, the TB index for all internal 3.5 inch SATA hard drives stands at $36.25 per TB (as of Nov 1, 2026 at 5:17 PM UTC).

New SAS hard drives on amazon.com, sorted by price per TB, as of Nov 1, 2026 at 5:17 PM UTC

We currently find 7 new SAS hard drives on amazon.com that are sold under the manufacturer's name. The selection is much smaller than for SATA. That makes the cheapest SAS drive about 21.4% cheaper per TB than the cheapest Exos with SATA (Seagate Exos X18 18 TB, $39.56 per TB, 18 TB). The TB index for SAS hard drives stands at $85.00 per TB.

On top of that come 5 used or refurbished SAS drives. The cheapest of them is the Seagate Constellation ES.2 3 TB at $16.00 per TB (3 TB). Used SAS drives can come from retired servers. For such offers, check the condition, the power-on hours and the seller's warranty. What matters there is covered in our guide Refurbished hard drives.

You will find every offer under SAS hard drives, and the SATA models under Internal 3.5" hard drives and Internal 2.5" hard drives.

When is SAS worth it over SATA?

SAS is worth it if you run a server or storage system with a SAS controller and SAS backplane, need 2 paths to each drive or hang many drives off one controller. For a PC, a home NAS or a small home server, SATA is the simpler choice.

The decision by use case:

In a home server with a SAS controller you can just as well use SATA drives. The SAS standard provides for that compatibility, and the selection of SATA drives is much larger. According to its data sheet, the Exos 7E10 comes in both versions. The cheapest Exos with SATA right now is the Seagate Exos X18 18 TB at $39.56 per TB. For a classic NAS, the NAS lines with CMR are the ones built for the job. Our guide Best NAS hard drive shows the options.

Are SAS hard drives faster than SATA hard drives?

With the same mechanics, only slightly. According to the data sheet, the SAS version of the Exos 7E10 reads 236 MB/s and the SATA version 215 MB/s. Faster on random access are SAS drives with 10,000 RPM, such as the Seagate Enterprise Performance 10K, at the cost of small capacities.

A hard drive's speed mostly depends on spindle speed, areal density and cache. The interface only becomes a bottleneck when many drives share one link or an SSD is attached. One example is the Seagate Enterprise Performance 10K with 10,000 RPM and SAS. Its ST1200MM0088 has 1.2 TB according to the data sheet. Drives like this usually cost a lot more per TB than large 7,200 RPM drives. For fast random access, an SSD is the alternative today. How SSDs and hard drives differ is explained in our guide SSD vs HDD.

Are SAS hard drives more reliable?

Not automatically. For the Exos 7E10, Seagate states the same MTBF of 2 million hours, the same annualized failure rate of 0.44% and the same 5 year warranty for SAS and SATA. SAS adds protection on the transfer, with T10 DIF and 2 paths to the drive.

Reliability mostly depends on the product line. An enterprise drive like the Exos is built for always-on operation with both SAS and SATA. A desktop drive like the BarraCuda is rated for only 2,400 power-on hours per year according to its data sheet. A SAS vs SATA comparison is therefore often an enterprise vs desktop comparison, and the difference comes from the line. If reliability matters to you, compare workload, power-on hours and warranty on the data sheet. How long hard drives last on average is shown in our guide How long hard drives last, and what a desktop drive is rated for in Seagate BarraCuda.

What about SAS for SSDs and NVMe?

SAS also exists for SSDs, mostly in the 2.5 inch form factor. Next to them are server SSDs with NVMe, connected directly over PCI Express, often in the U.2 form factor. For hard drives, SAS and SATA are the common interfaces.

According to the SCSI Trade Association, the 24G SAS specification was completed in 2017. In July 2024 it presented the next step, 24G+ SAS, and stressed compatibility with SATA. For you as a buyer this means: a SAS controller today accepts SAS and SATA drives, and a new controller works with older SAS drives. If you are looking for server SSDs, you will find U.2 models with NVMe under U.2 and U.3 SSDs.

How do I recognize a SAS hard drive?

By the data sheet and the model number: Seagate lists the interface as "12Gb/s SAS" or "SATA 6Gb/s". For the 6 TB Exos 7E10, the SAS version is the ST6000NM001B and the SATA version the ST6000NM000B. Listing titles usually include "SAS" and "12Gb/s".

With used server drives, also watch for these points:

• Part number from a server maker: Some listings show a server maker's part number, such as Dell's, instead of the drive maker's model number. Whether such a drive works in your system is in your controller manual.
• Form factor: SAS drives come in 3.5 and 2.5 inch. Check which size your bays take.
• Sector format: 512n, 512e or 4Kn has to match your controller and system.
• Warranty: Ask the seller about the warranty before you buy.

You check the condition of a used drive after installing it with its SMART values. How that works is explained in our guide Check hard drive health.

How does ratioDB compare SAS hard drives?

ratioDB regularly pulls the amazon.com prices for every listed hard drive and converts them to price per TB, with 1 TB equal to 1,000,000,000,000 bytes. SAS hard drives have their own list with their own TB index, the median of the 10 cheapest new offers.

We match series, spindle speed and recording method to every model number using the manufacturer's data sheet. Where the data sheet does not say, the tables show "n/a". The tables in this guide only show new single drives sold under the manufacturer's name. Used and refurbished offers are labeled and never count toward the index. ratioDB does not test drives itself. All rules are on the Methodology page, and every hard drive is listed under Hard drive prices per TB.