SAS (Serial Attached SCSI)

Anyone who opens a server often finds hard drives that look like normal SATA drives at first glance but have a different connector. These are usually SAS hard drives. For decommissioning the difference matters, because not every erasure tool speaks SAS.

What is SAS?

SAS is the successor to the parallel SCSI interface, which was long the standard in servers. Like SATA, SAS is serial, that is, with few lines and a point-to-point connection. The command set, however, comes from the SCSI world. SAS drives are used mainly in rack servers, storage systems, and drive enclosures.

The generations are named after their data rate, for example SAS-3 with 12 Gbit/s and SAS-4, also called "24G SAS". There are SAS hard drives (HDD) and SAS SSDs. High-performance SAS hard drives spin at 10,000 or 15,000 revolutions per minute. For large capacities there are so-called nearline SAS drives with 7,200 revolutions. Many SAS drives for data centers are also available as a self-encrypting variant, which opens up additional options when erasing.

SAS and SATA compared

Feature	SAS	SATA
Use	Servers, storage, data center	PCs, notebooks, simple servers
Command set	SCSI	ATA
Connections	Two ports possible (dual port) for fail-safe connection	One port
Compatibility	SAS controllers can operate SATA drives	SATA controllers cannot operate SAS drives
Erase commands	SCSI SANITIZE, FORMAT UNIT	ATA Secure Erase, ATA Sanitize

More on the counterpart in the entry SATA.

What to note when retiring devices

• Suitable hardware: SAS drives cannot be connected to a normal PC with a SATA connector. Erasing requires a SAS controller or special erasure stations.
• Mind the RAID: In servers, SAS drives usually run in a RAIDarray. Every individual drive is erased, not just the logical volume that the operating system sees.
• Drive commands: Many SAS drives support the SCSI SANITIZE command, which also reaches areas that remain hidden during overwriting. More in the entry Sanitize command.
• Sector size and formatting: SAS drives from storage systems are sometimes formatted with special sector sizes. Erasure software must be able to handle this.

How the sale of servers relates to data erasure is shown in our guide sell used servers.

SAS drives and Second IT

Second IT erases HDDs and SSDs from PCs, laptops, and servers with the Blancco Drive Eraser, including hidden areas such as HPA and DCO as well as remapped sectors. For storage environments, Blancco LUN Eraser is also available. Every drive receives a digitally signed erasure certificate with a serial number. More on the certified data deletion.

Frequently asked questions about SAS

Can I connect a SAS hard drive to a PC?

Not directly. SAS drives need a SAS controller. The reverse works: SATA drives can generally be operated on SAS controllers.

Is a SAS hard drive better than SATA?

It is built for different requirements: continuous operation, many drives on one controller, fail-safe connection. For a workstation PC SAS offers no advantage, in a server it does.

Do I have to remove SAS drives from the RAID to erase them?

Not necessarily, but every drive must be erased individually and documented. If only the logical RAID volume is overwritten, spare drives or individual areas can remain untouched.

How do I erase SAS hard drives securely?

You need a SAS controller or a special erasure station and erasure software that supports SCSI commands such as SANITIZE or FORMAT UNIT. Every drive is erased and documented individually, even if it runs in a RAID.

What does nearline SAS mean?

Nearline SAS drives are SAS hard drives for large capacities. They spin at 7,200 revolutions per minute. High-performance SAS hard drives spin at 10,000 or 15,000 revolutions per minute.