SAS Solutions for All Server and Storage Applications

Author: David So, Product Marketing Manager and Bruce Grieshaber, Product Manager

Over the past several years, the SCSI Trade Association (STA) has gone to great lengths to educate the public on the features and benefits of Serial Attached SCSI (SAS). STA has even sponsored a series of plugfests at the University of New Hampshire’s InterOperability Lab to ensure the compatibility of different vendors’ SAS products with one another, thereby easing the adoption and integration of SAS into the marketplace. The result is that SAS has indisputably been accepted as the Direct Attached Storage (DAS) interconnect of choice. Since SAS’ inception, the storage industry has announced a wide array of SAS infrastructure components as well as SAS-based servers and external storage systems. Today, most server platforms use SAS for the internal drive interconnect. And with the ability to support SAS and Serial ATA (SATA) hard drives, it is quickly becoming the mainstream disk drive interface for external storage enclosures.

With all of the performance, scalability, and flexibility benefits that SAS offers, it is easy to understand why SAS is being adopted so readily as the next generation of the ubiquitous SCSI interface. The demands on enterprise data centers worldwide are ever increasing with the need for greater amounts of storage (Sarbanes-Oxley and HIPAA are two reasons) plus higher performance. SAS vendors are expected to offer all this at approximate price parity with previous generations of the technology. Another factor is industry desire for lower power consumption and greater restrictions on space within the data center. Add all of these requirements together, and SAS is the only technology that can meet the growing storage demand.

The quick adoption of SAS can partly be attributed to the numerous companies offering SAS products. Among those vendors are LSI, Adaptec, Emulex, Fujitsu, Hitachi GST, HP, Dell, IBM, Intel, Maxim, Molex, PMC-Sierra, and Seagate, with products including ICs, host bus adapters (HBAs), cables, connectors, 2.5″ and 3.5″ disk drives, servers and storage enclosures.

Table 1 below shows the number of companies that currently offer various SAS components.




LSI – SAS ICs, HBAs, and RAID Adapters
LSI offers a broad range of SAS solutions in the industry today, ranging from controller and expander ICs, to HBAs and RAID adapters, to external storage, to active-active multiplexers, to drive controller solutions. LSI was actually the first to introduce PCI-X-to-SAS controller ICs to the market with both four- and eight-port SAS versions. Those were followed by PCI Express-to-SAS controllers. Providing unprecedented performance and scalability for server DAS and external storage systems environments, these SAS controller ICs meet the increasing bandwidth and flexibility demands of blade server environments and high-end server and storage subsystems.

Expanders fulfill the scalability feature of SAS by allowing creation of SAS domains with more than 16K end devices. Companies offer expanders from six ports to 36 ports for implementation of DAS in servers as well as in external storage enclosures with up to 24 (and sometimes even 48) disk drives. Expanders can be cascaded to form even larger topologies. LSI offers 12-port, 28-port, and 36-port expander ICs. The 28-port SASx28 and 36-port SASx36 expanders incorporate an ARM processor that can be used for enclosure management as well as extended SAS SMP functions, and support SAS zoning for storage partitioning. Much like the controller ICs, each expander IC supports 3Gb/s SAS and SATA data transfers per port, SAS and SATA drive connectivity, and wide-port support for aggregated bandwidth across multiple SAS phys.

The SASx36 expander is the basis for LSI’s SAS switch, which extends the capabilities of SAS beyond a SCSI replacement in DAS environments to an actual fabric infrastructure. By providing an interconnect from multiple servers to one or more external storage systems, the SAS switch enables medium-sized businesses to take advantage of a cost-effective and scalable high-performance storage network. Through the use of zoning, multiple storage domains can be configured.


Figure 1: LSI’s SAS Product Portfolio


LSI’s family of SAS HBAs (all based on the controller ICs mentioned above) are available with PCI-X and PCI Express host interfaces and four- and eight-port SAS connections with a wide variety of internal and external connector options to support any application or system topology. Many of these HBAs also support LSI’s Integrated RAID (IR), which is a highly-integrated, hardware-based RAID solution ideal for systems requiring redundancy and high availability but not needing a full-featured RAID implementation. IR includes Integrated Mirroring and Integrated Striping for support of up to ten physical disk drives. Table 2 below shows some of the production LSI HBAs and their various SAS connector offerings.


Table 2: LSI’s SAS Host Bus Adapters


LSI also has a full line of MegaRAID® SAS adapters featuring external and internal storage connectivity and delivering high-performance, flexible, fault-tolerant data protection that is scalable for both SAS and SATA configurations. The latest additions to this family are the low-profile, eight-port internal MegaRAID SAS 8708ELP and the low-profile MegaRAID SAS 8888ELP adapters, both based on LSI’s proven SAS1078 PCI Express to eight-port SAS RAID-on-a-Chip (ROC) IC. With selectable connectors, the 8888ELP serves multiple deployment needs. Users may select one of three connector configurations: two internal, two external or one of each. Both adapters offer 3Gb/s throughput per port, the ability to intermix SAS and SATA devices in the same array, and support of SAS expanders and SATA native command queuing (NCQ). Additionally, each adapter provides RAID 6 support to protect against data loss in the event of dual-drive failures. This is a critical feature in SAS environments where systems are often deployed with higher-capacity, yet lower-reliability SATA drives. The MegaRAID SAS 8708ELP and 8888ELP adapters also offer battery backup options to protect the integrity of cached data. By providing power in the event of a brief power outage or complete AC power failure, MegaRAID battery backup units provide an inexpensive alternative to using an uninterruptible power supply.

These second-generation MegaRAID SAS cards are supported by the MegaRAID Management Suite™ of software – a complete spectrum of applications and tools including next-generation pre-boot and advanced online RAID management utilities. This suite of applications features a variety of configuration options and SAS topology views from the system host, controller, and disk enclosure down to the logical and physical drive level. This allows administrators to efficiently configure, monitor, and manage RAID volumes locally or over the network.

AAMUX™ ICs and Interposer Cards
Based on LSI’s patent-pending AAMUX™ technology, the LSISS1320 and LSISS1350 Active-Active Multiplexer ICs, as well as their corresponding LSISS9132 and LSISS9135 interposer cards, enable manufacturers to build economical enterprise storage systems that can accommodate low-cost, high-capacity SATA hard drives without sacrificing reliability, manageability, or data availability. In response to enterprise IT initiatives such as Information Life-cycle Management (ILM), infrastructure ROI, and regulatory compliance, storage system vendors must address the increasing pressure to deliver more storage capacity for less money. LSI AAMUX technology makes this possible by enhancing SATA drives with essential enterprise-class features on par with either SAS or Fibre Channel (FC) drives.

LSI’s AAMUX technology enables single-ported SATA drives to connect like native dual-ported drives for use in enterprise storage systems using SAS expanders supporting the SATA Tunneling Protocol (STP), and in systems using FC-to-SATA routers. The AAMUX™ ICs and interposer cards bring true active-active multiplexing to the SATA drive with both ports simultaneously available, much like dual-ported FC or SAS drives. A dual-ported active-active SATA drive solution results in much higher performance and reduced system development costs when compared to the previous active-passive approach. Because software failover is no longer required, this approach greatly simplifies system software complexity and manageability.

SAS External Storage Systems
LSI’s storage systems include the Engenio 1333 and 1331, featuring SAS-to-SAS external RAID arrays for shared DAS infrastructure. The model 1331 and 1333 systems feature a modular design that creates an affordable entry-point without sacrificing future scalability, enabling configured system capacity to be easily matched to initial amounts of storage needed and scaled up as storage requirements grow. Dual-active controllers with up to 12 drives in a 2U enclosure create a fully-featured and reliable storage system. And when capacity and/or functionality requirements change, the 1333 supports up to 36 additional drives and offers key-enabled features for additional functionality.

The multi-ported model 1333 is an ideal entry-level solution for clustered topologies and readily meets the external two-node clustering requirements of end users. Clustering allows multiple servers to share access to data stored on a single storage system and keeps applications running on a secondary server should the primary fail.

These systems enable growing businesses to reap the benefits of shared storage including consolidation, unified management, data protection features, and increased efficiencies within the IT infrastructure. Managed by Simplicity Storage Manager software, the systems bring an intuitive, task-based management structure that significantly reduces the complexity of installation, configuration, management, and diagnostic tasks, along with feature-rich capabilities to enable deployment of advanced data protection strategies.

LSI offers a broad portfolio of SAS storage solutions, addressing every segment of the market. By offering best of breed SAS technologies, assured interoperability, and single vendor support, LSI is the silicon-to-systems supplier of choice for OEMs and SMBs that want to deliver a broad set of storage solutions.

For more information about LSI Serial Attached SCSI products, please visit

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