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SAS - The reliable data transfer standard for servers and storage systems

As a widely used and capable technology for the connection of hard disks in servers and storage systems, SAS (Serial Attached SCSI) is an established standard that is characterised by the combination of high transfer rates, scalability and reliability. It meets the demands for high-performance, high-availability storage solutions in data centres and enables companies of all sizes to benefit from the extensive management capabilities of scalable data storage in growing IT infrastructures. Depending on the application and performance required, both traditional HDDs (Hard Disk Drives) and SSDs (Solid State Drives) with SAS connectivity can be used as storage media, ensuring fast data processing even for demanding applications such as databases or virtualisation. In order to keep up with the advance of digitalisation and ever-increasing data volumes, the standard based on the SAS SCSI Protocol (SSP) has been continuously developed through various generations, enabling higher transfer rates with each new version of the interface.

SAS generations with increasing transfer rates:

  • 2004: SAS-1 with up to 3 Gbit/s
  • 2009: SAS-2 (6G) with up to 6 Gbit/s
  • 2013: SAS-3 (12G) up to 12 Gbit/s
  • 2017: SAS-4 (24G) with up to 22.5 Gbit/s

The different generations are basically compatible with each other, but in a system with mixed standards, only the speed of the slowest connection version will be achieved. For example, SAS-3 generation hard drives can be used in servers that support SAS-2, but will not achieve their maximum performance. However, such a configuration may still make sense in certain scenarios, for example if you are planning to purchase a new generation of servers and want to continue using your existing drives. Another advantage of the SAS connection is that it is compatible with SATA hard drives (Serial Advanced Technology Attachment), which can therefore still be used when changing systems and communicate with the newer standard via STP (Serial ATA Tunneling Protocol).

The SAS interface enables high scalability and extensive storage management

One of the key features of SAS is its excellent scalability. If server configurations support the standard, the storage capacity of the systems can be flexibly adapted to changing requirements by adding and removing hard disks with the appropriate trays in the drive cage, often even during operation. Depending on the model, SAS controllers typically feature two or four ports that can be used to directly connect drives and backplane boards. If these are not sufficient, additional expander cards can be added to increase the number of SAS ports.

In addition, through the SAS Management Protocol (SMP), expander technology offers the potential to build large data storage systems with hundreds or even thousands of hard drives. In theory, edge expanders bundle up to 128 end devices, or SAS addresses, onto a single SAS cable, allowing a far greater number of devices to be supported than the RAID controller provides ports for. In practice, however, edge expanders are usually only available for up to 36 end devices, although up to two expanders can be used on one controller. For particularly large storage domains, additional fanout expanders can be installed between the controller and the edge expander. Although these do not allow direct connection of end devices, they do fan out the connection into 128 ports, each of which can be used by an edge expander. The use of both types of expander theoretically allows over 16,000 SAS devices to be used, enabling storage infrastructure to be scaled to meet the needs of complex environments such as data centres.

As SAS hard drives typically have two ports compared to SATA models, the standard also offers advanced features in this area. For example, to increase performance, both ports can be bundled to double the transfer rate, which in the case of SAS-3 enables a data rate of up to 24 Gbit/s by bundling connections. Alternatively, the ports can be used for dual porting. In this case, the ports of the hard drive are connected to different host adapters, enabling redundant structures as two independent systems can access the drive. Overall, the SAS standard offers high reliability and data integrity with error correction, data verification and redundancy technologies. This contributes to secure data transfer and storage, efficient management of large storage capacities and high availability.

Refurbished SAS drives and accessories at affordable prices - ServerShop24

In order to adapt your storage systems to increasing requirements, used and carefully checked SAS hard drives are in many areas a cost-efficient and sustainable alternative to the purchase of new drives. High-quality enterprise and data centre hard drives that have already been in use can often fully meet your requirements, protecting your budget with an excellent price-performance ratio and the environment at the same time, as the amount of electronic waste is not further increased by the continued use of functional hardware.
With over 10 years of experience, we are your competent partner for professionally refurbished used servers, storage systems and network equipment. In our extensive stock, you will find a wide range of ready-to-ship equipment from leading manufacturers, as well as the matching accessories, spare parts and components to customise your systems. You can receive your order with the shortest possible delivery times due to fast shipping from our stock. If you have any questions about products and configuration options, our friendly and experienced support team is available to assist you. Use one of the many ways to contact us - we will take care of your request!