SAS FAQs


Q: What does SAS stand for?
A: SAS is an acronym for Serial Attached SCSI.

Q: What is SCSI?
A: SCSI is a type of data bus allowing for the transfer of data between a computer and peripheral devices. It was the first intelligent data bus relieving the CPU from the burden of processing I/Os between the computer and its peripherals.

Q: What is SAS?
A: SAS is a point-to-point serial architecture that is far simpler than its parallel predecessor SCSI, yet offers significantly higher throughput (up to 6-Gb/sec) as well as better scalability.

Q: What is the difference between Serial Attached SCSI and Parallel SCSI?
A: Serial Attached SCSI (SAS) is an evolutionary development of Parallel SCSI, a proven technology that's been the foundation of enterprise storage for over two decades. SAS leverages the rock-solid reliability of Parallel SCSI while offering dramatic improvements in performance, scalability and compatibility.

Q: What's the difference between Serial Attached SCSI and Serial ATA?
A: Serial Attached SCSI is an enterprise-class solution that goes beyond its interface to deliver the superior performance, reliability and scalability demanded in mission-critical applications. Serial ATA is primarily a desktop-class solution suitable for use in light-duty environments where low cost is the highest priority.

Q: Are SAS and Serial ATA compatible?
A: Yes, compatibility with Serial ATA is a core feature of Serial Attached SCSI. SAS backplanes and Host Bus Adapters (HBA) are fully compatible with Serial ATA, enabling connectivity for both types of drives on a common backplane, lowering infrastructure costs. SAS enclosures offer tremendous flexibility for growing businesses that can deploy Serial ATA drives when storage requirements are modest, and then seamlessly add SAS drives as evolving business needs dictate. This guarantees the freedom to specify the optimal drive for the application: SAS for transactional/online performance and reliability, Serial ATA for nearline and backup/restore duties.

Q: When do I use SAS, SATA?
A: SAS provides SCSI-like price, performance, and reliability points between Fibre Channel and SATA to give you more flexibility in choosing solutions. SATA configurations offer performance trade-offs. Though SATA provides the lowest initial acquisition cost, it does not offer mainstream enterprise feature functionality. SAS, however, delivers a compelling value proposition for the mainstream IT datacenter — the benefits of lower costs, high performance, and flexible hardware configurations, improved margins and customer satisfaction on nearly any storage solution. Keep in mind also that if you are using SAS, you can continue to use that enclosure for a different purpose as storage needs change over time, creating a compelling TCO value proposition.

Q: How do I choose between Fibre Channel and SAS technology?
A:

If you have invested in a Fibre Channel infrastructure, beginning your transition to SAS enclosures now allows you to increase storage scalability and flexibility, while maintaining Fibre Channel connectivity to the network. If you have invested heavily in an extensive Parallel SCSI infrastructure that you are looking to maintain, for the moment, it makes sense to continue to rely on your trusted SCSI solutions. Think about transitioning to SAS sooner rather than later if you:

  • Want to simplify the datacenter — standardize on a SAS-based server or storage chassis
  • Are seeking a long-term strategic storage solution
  • Need a lower TCO
  • Need high-performance, enterprise features and value pricing
  • Are ready to adopt the new standard instead of investing further in an Ultra320 standard that has reached the end of its development
  • Need the flexibility of SAS for a multi-use storage solution. If shared storage is required then Fibre Channel is the technology of choice. If transfer speeds are more important than sharing storage, then SAS is preferable.

Q: How is firmware upgraded?
A: Firmware is easily flashed/downloaded onto the ExpressSAS Adapters. The process takes only minutes to complete. Easy field upgradeability ensures that customers can always be running with the latest capabilities and updates available. The latest firmware versions are obtainable on our website.

Q: How difficult is it to set up the ExpressSAS Adapter?
A: Thanks to the one-click installation design of ExpressSAS Adapters, setup of RAID and other options has never been easier. The easy-to-use setup wizard provides a quick and complete setup of the ExpressSAS Adapter.

Q: Can I add new features to the ExpressSAS Adapter, even after it has been in use at my location?
A: We develop features for our products even after they are released. With customer feedback and information from our marketing team, we add new features which are available to customers usually for no additional charge. Updated firmware, when available, will be located on our website. Always backup your current data before updating the firmware on any ExpressSAS Adapter product.

Q: What industry certifications are available?
A: All ExpressSAS HBAs & RAID Adapters undergo rigorous testing to ensure flawless operation in a wide variety of storage environments. A list of qualifications is available on our interoperability page. For additional information, or if your particular device isn't listed, contact ATTO technical support. ATTO works closely with industry partners to ensure compatibility.

Q: What is the warranty on the ATTO ExpressSAS Adapters?
A: ATTO ExpressSAS Adapter products come with a three year warranty with technical telephone support available.

Q: What is a Serial Attached SCSI expander?
A: Expanders are the key to Serial Attached SCSI's remarkable scalability. Each of these low-cost switches enables up to 128 point-to-point connections to be made off a single HBA/enclosure, and a total of 16,384 SAS devices can be aggregated while preserving performance and reliability. By contrast, Parallel SCSI imposes a limit of fifteen devices per SCSI chain and severely limits total cable length.

Q: Does SAS replace Fibre Channel?
A: No. Serial Attached SCSI and Fibre Channel are both advanced, enterprise-class solutions with specific attributes that influence their suitability for a given application. SAS offers outstanding performance and exceptional scalability on a local level. Fibre Channel is well suited for large enterprise use [e.g., a Storage Area Network (SAN)] due to its support of up to 16 million addresses and maximum cabling distance of ten kilometers.

Q: What is the ATTO ExpressSAS Host Adapter?
A: ExpressSAS 6Gb/s SAS/SATA host bus adapters offer the fastest available connection to direct-attached SAS or SATA storage. The impressive speed of the ExpressSAS family of next-generation 6Gb/s SAS HBAs delivers a future-proof solution for data-intensive IT and digital media applications such as tape backup, data warehousing, high-definition video, cloud computing, business intelligence, post -production and digital film production. ExpressSAS 6Gb/s HBAs offer high-performance, a field serviceable design, flexibility options and a low profile form factor for use in server and workstation applications

Q: What is the ATTO ExpressSAS RAID Adapter?
A: The ATTO ExpressSAS RAID Adapter offers a unique combination of blazing-fast performance and flexibility. Connect individual disks, JBODs or RAID systems and instantly increase performance and reliability. In addition, you can expand RAID groups and add storage on-the-fly, growing as your needs grow. The ATTO ExpressSAS RAID Adapter is a unique solution that leverages ATTO's engineering expertise in data management. The ExpressSAS RAID Adapter offers high-performance features such as hardware-based RAID and field serviceable design, all in a true low profile form factor.

Q: What RAID levels are supported?
A: The ExpressSAS RAID Adapter supports JBOD, RAID 0/1/4/5/6/10/40/50/60 levels allowing users to meet a variety of data management application needs. Also included is ATTO's exclusive DVRAID™. The ExpressSAS Host Adapter supports software level RAID with Express Power Center.

Q: Is the ExpressSAS RAID Adapter suitable for video applications?
A: The ExpressSAS RAID Adapter is optimized for video needs. The ExpressSAS RAID Adapter supports a wide selection of video solutions and configurations and has industry-proven results to support this. There are three key aspects to supporting a video application – 1) performance, 2) software and 3) interoperability. The ExpressSAS RAID Adapter offers all three.

Q: How many streams of video and audio are supported by the ExpressSAS RAID Adapter?
A: The smooth data streaming of the ExpressSAS RAID Adapter supports multiple streams of high-definition video as well as multiple tracks of constant audio streaming. The actual number of streams is dependent on the number and types of drives used.

Q: How does the ExpressSAS RAID Adapter achieve its blazing-fast performance in RAID configurations?
A: RAID applications are the most taxing on storage subsystems. These calculations (called XOR processes) ensure redundancy but are "compute intensive". The ATTO ExpressSAS RAID Adapter utilizes hardware to complete the XOR calculations. This removes the task from the processors running the storage and places the workload on components optimized for the duty. ATTO uses patented technology coupled with custom software to accomplish this. ATTO has many years of RAID storage development experience that results in enhanced performance in the ExpressSAS RAID Adapter.

Q: What separates the ATTO ExpressSAS RAID Adapter from off-the-shelf RAID solutions?
A: The ExpressSAS RAID Adapter utilizes ATTO patent-pending technologies, rather than off-the-shelf RAID solutions, to provide unsurpassed performance and category-leading flexibility. The ExpressSAS RAID Adapter features Advanced Data Streaming (ADS™) Technology – resulting from years of research and design. ADS is the heart of the ExpressSAS RAID Adapter. The RAID adapter contains a combination of custom Application-Specific Integrated Circuits (ASICs), processors and proprietary embedded software to make ADS processing technology a reality.

Q: How many drives does the ExpressSAS RAID Adapter support?
A: The ATTO ExpressSAS RAID Adapter supports up to 256 end target devices including any combination of disks, JBODs and RAID arrays.

Q: How many drives does the ExpressSAS Host Adapter support?
A: The ATTO ExpressSAS Host Adapter (non-RAID) can support up to 2,048 end-devices including any combination of disks, JBODs, tape libaries, and RAID arrays. A total of 128 virtual devices or RAID groups can be defined.

Q: Is SAS a proven technology?
A: Yes. In 2001, less than nine months after the initial brainstorming meeting, membership in the group working on Serial Attached SCSI expanded to almost 30 companies. A key goal of the group was to outline the general architecture and features of the interface and then move the detailed development of the document describing the interface to an open and unencumbered forum. After preliminary work was completed, the SAS project was submitted to the ANSI INCITS T10 technical committee for development as a national (and later, international) standard. The project was approved and, after significant work by the technical committee, a version of the draft standard passed letter ballot at the end of 2002 for completion of processing so that the draft would become an ANSI standard in 2003.

Q: What environments use SAS?
A:

SAS environments include:

Application: High-availability, high-reliability internal storage for workstations and servers.

This solution uses a SAS RAID Adapter with either internally connected point-to-point drives, or using a four-drive-bay, 5.25" internal enclosure, and is ideally suited for:

  • Applications that require high availability through mirroring
  • High-reliability solutions through the use of SAS drives
  • High-performance demands that can take advantage of SAS throughput
  • Applications that require point-to-point connections within the server chassis with simplified cabling
  • CAD/CAM/CAE or modeling applications
  • Small capacity databases
  • Workstation-based video and audio capture and editing

Application: Easy scalability for databases and other continually growing datasets

As illustrated, this solution combines the highest performance, highest availability though a comprehensive RAID set, and highest scalability available for Direct Attached Storage (DAS). For higher capacity needs, a SAS external JBOD enclosure can be connected to the HBA.

SAS provides higher scalability than the existing SCSI standard and is similar to Fibre Channel. Simply daisy chain JBODs to the RAID card to add capacity. With the external enclosure and SAS drives, this solution is ideal for enterprise-class primary storage applications with high availability needs, including data warehousing, databases, and decision support, in any demanding application environment.


Q: What other equipment are the ExpressSAS Adapters interoperable with?
A: The ATTO ExpressSAS RAID and Host Adapters are tested with an extensive list of third-party equipment such as expanders, disk drives, tape drives, SSD's and ISV applications such as backup, video and audio. For a complete listing, see the Interoperability Matrix on our website.

Q: What regulatory and safety certifications have the ExpressSAS Adapters been tested for?
A:

ExpressSAS Adapters are thoroughly tested for compliance with worldwide regulatory agency, safety and shipping certifications. Certifications include:

  • FCC
  • CE
  • RoHS compliance

Q: What is RoHS?
A: RoHS represents the Restriction of Hazardous Substances in electrical and electronic equipment. It is a European Union directive intended to preserve the environment. The directive places limits on the importation of these six substances: Lead, Mercury, Cadmium, Chromium, PBBS and PBBEs. The restrictions were enforced in Europe and Asia in July 2006 with the restrictions to grow to other geographic locations in the future.

Q: Does ATTO offer RoHS compliant products?
A: ATTO ExpressSAS Adapters and other product offerings are RoHS compliant.
Top