Appendix A: Introduction to SAS 89

Terminology Used in This Chapter

For convenience, SAS HBAs and SAS RAID controllers are referred to generically in this chapter as SAS cards. HBAs, RAID controllers, disk drives, and external disk drive enclosures are referred to as end devices and expanders are referred to as expander devices.

For convenience, this chapter refers to end devices and expander devices collectively as SAS devices.

What is SAS?

Legacy parallel SCSI is an interface that lets devices such as computers and disk drives communicate with each other. Parallel SCSI moves multiple bits of data in parallel (at the same time), using the SCSI command set.

SAS is an evolution of parallel SCSI to a point-to-point serial interface. SAS also uses the SCSI command set, but moves multiple bits of data one at a time. SAS links end devices through direct-attach connections, or through expander devices.

SAS cards can typically support up to 128 end devices and can communicate with both SAS and SATA devices. (You can add 128 end devices—or even more—with the use of SAS expanders. See page 93.)

Note: Although you can use both SAS and SATA disk drives in the same SAS domain (see page 93), we recommend that you not combine SAS and SATA disk drives within the same array or logical drive. The difference in performance between the two types of disk drives may adversely affect the performance of the array.

Data can move in both directions simultaneously across a SAS connection (called a link—see page 90). Link speed is 300 MB/sec in half-duplex mode. Therefore, a SAS card with eight links has a bandwidth of 2400 MB/sec.

Although they share the SCSI command set, SAS is conceptually different from parallel SCSI physically, and has its own types of connectors, cables, connection options, and terminology, as described in the rest of this chapter.

To compare SAS to parallel SCSI, see How is SAS Different from Parallel SCSI? on page 94.

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Adaptec 2268300R manual Terminology Used in This Chapter, What is SAS?

2268300R specifications

The Adaptec 2268300R is a robust and versatile RAID controller designed for enterprise-level storage needs. Ideal for environments demanding high availability, performance, and data protection, this controller provides organizations with the ability to manage large volumes of data while ensuring reliability.

One of the standout features of the Adaptec 2268300R is its support for various RAID levels, including RAID 0, 1, 5, 6, 10, 50, and 60. This flexibility allows users to choose the configuration that best suits their performance and redundancy requirements. By combining multiple drives into a single logical unit, the controller enhances data throughput and ensures data safety through redundancy.

The controller is built on a SATA and SAS architecture, allowing it to connect directly to both SATA and SAS drives. This broad compatibility is crucial for businesses looking to leverage existing hardware while also scaling their storage infrastructure. The Adaptec 2268300R is equipped with a powerful onboard processor that significantly boosts performance, driving down latency and increasing transaction speeds across connected drives.

Additionally, the Adaptec 2268300R features cache memory with a non-volatile option that enhances data integrity during unexpected power outages. This feature is essential for mission-critical applications where data loss can have severe repercussions. Moreover, the controller supports advanced caching algorithms, optimizing write and read performance to meet the demands of modern applications.

The controller also integrates seamlessly with Adaptec's management suite, providing users with a graphical interface to monitor and manage their storage solutions effectively. The web-based management tool allows administrators to configure RAID settings, monitor disk health, and perform troubleshooting, all from a centralized platform.

Security is another critical aspect of the Adaptec 2268300R. The controller comes equipped with encryption capabilities, enabling users to secure sensitive data at rest—protecting information from unauthorized access. Furthermore, with features like hot-spare drive support and automatic rebuilds, the controller assures continued operation even in the event of a disk failure.

In conclusion, the Adaptec 2268300R is a powerful RAID controller that delivers significant advantages in performance, flexibility, and reliability. With its support for multiple RAID levels, SAS and SATA compatibility, robust caching, and advanced management tools, it stands out as an ideal solution for businesses needing to safeguard and manage their vast data assets efficiently. Whether for enhancing data security or optimizing storage performance, the Adaptec 2268300R remains a sound choice in today’s data-driven landscape.