SAS Innovates with the Evolving Enterprise

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SAS Innovates with the evolving enterprise

By Cameron T. Brett, Secretary, SCSI Trade Association, PMC-Sierra, Inc.

ince the turn of the millennium, enterprise IT and datacenters and scalable storage architectures can be designed to ﬁt a vast set Shave quickly evolved and adapted to new demands of larger of application and uptime requirements. These longer connectivity databases, internet/intranet/extranet, vast email repositories and the options include optical and active copper. Active copper can extend new norm of Web 2.0’s unstructured data. These demands continue to 20 meters and uses the currently available SFF-8088 mini-SAS to push data requirements to new heights: reliability, performance, connector. To extend to 100 meters, optical is the connectivity option. ease of use, ability to scale and management of the data domain. It uses a new version of the mini-SAS connector in an HD package, Serial Attached SCSI (SAS), and the underlying small computer enabling 2x the signals in the same footprint as mini-SAS. This SFF- system interface (SCSI) protocol has evolved and adapted to meet 8644 connector is a “managed” cable, which allows management these demands. tools to monitor and manage cable and connection functionality.

From doubling performance at its core to embracing solid state disks SSDs Shine with SAS (SSDs) and ﬂash storage and enabling ﬂexible architectures, SAS SSDs are changing the way datacenters look at performance. Acting continues to be the storage technology best suited for the enterprise. as a caching layer, an incremental amount of SSDs used with a typical HDD volume can easily boost performance many times over. A minor 12Gb/s SAS – Performance Doubles Again investment can result in fantastic returns. This investment in SSDs will 2012 marks the 31st year of SCSI as a standard interface. only be as good as the underlying technology. Performance has doubled every few years and the trend continues with 12Gb/s SAS. Announced in October 2011, 12Gb/s SAS is more Flash memory today is less understood as enterprise storage than than just a performance kick. It preserves and optimizes existing existing HDD storage and not as easily managed. SAS, with the SCSI investments in SAS storage with backward compatibility. 3Gb/s and protocol, provides the extra layer of reliability and robustness that 6Gb/s SAS and SATA devices will continue to be fully functional in a makes SSDs better suited to the enterprise. SCSI is enterprise proven 12Gb/s SAS environment. This SAS generation will better utilize the and is very well understood by developers and datacenter managers. bandwidth by aggregating 6Gb/s SAS devices to fully use a 12Gb/s Currently used management and RAID tools will seamlessly work with SAS link. As shown in Figure One, Input/output operations (IOPs) SAS-based SSDs and keep the whole storage infrastructure intact. continue to improve to over 1 million, more than doubling over 6Gb/s SASs 450K IOPs of raw performance. With new SSD behaviors and performance to manage, new SCSI commands are being created, some of which are implemented today. The wide data pipes of 12Gb/s SAS lay the plumbing for a high The way data is stored and managed on HDDs does not work for performing fabric within the data center. Combining 12Gb/s SAS SSDs. Flash memory will wear out over time, depending on usage. and longer cable options with SAS Advanced Connectivity, reliable Flash cells are rated for a certain number of program/erase cycles,

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with the less costly type of flash (MLC) being rated for much fewer 12Gb/s SAS backplane connector), MultiLink SAS creates a x4 wide program/erase cycles than the more expensive, but higher rated SLC solution which can push data faster than ever before in both IOPs flash. These new commands help to ensure the program/erase cycles and MB/s measurements. MultiLink will also work in a x2 mode with are more evenly distributed, better manage power consumption, the newly defined SFF-8639 multi-function connector which supports improve performance/latency and faster error handling to name a few. SATA, SAS, MultiLink and upcoming PCIe-based SSDs.

Combining the performance of ﬂash in SSDs with 12Gb/s SAS is a SCSI Express / SCSI Over PCIe (SOP) match made in heaven, allowing SSDs to perform to their potential. The SCSI Trade Association (STA) has recently accepted SCSI Look for today’s SSDs, performing in the 30,000 to 50,000 IOPs Express as a project. SCSI Express, recently known as SCSI Over range, to climb to well over 100,000 IOPs (4K, random read) per drive. PCIe, runs SCSI commands across a PCIe link rather than the usual SAS link. SCSI Express combines the enterprise-proven SCSI The most common use of SSDs in enterprise storage will be to use command set with the lower latency quality of PCIe to directly connect them as a cache for HDD storage. HDDs commonly “short stroke” to the host x86 processor, enabling SSDs to operate at their lowest to access only the fastest moving tracks on an HDD to maximize the latency possible. performance. This will bring HDD IOP performance up to 300 or 400 IOPs. The downside is that the storage capacity of that HDD will drop This innovation demonstrates the robustness of SCSI and its ability to to 25% or less of the total capacity of the drive. The use of SSDs as continue to be the enterprise technology of choice adapting to new cache or “Tier 0” storage will replace the need for short stroking. storage interfaces, such as PCI Express.

The HDD volume can be used to their maximum capacity, reducing Innovation….Again and Again the quantity of mechanical drives, which could increase system New data demands require continual innovation to keep up with uptime and data availability. and continue to protect critical data. SAS/SCSI is enterprise proven and adapts to these new demands for performance, reliability and MultiLink SAS management of enterprise data. With a keen ﬁnger on the pulse of To further enhance the performance capabilities of SAS, MultiLink was the customer, SAS/SCSI suppliers work together to innovate again introduced to widen the SAS pipeline connected to ﬂash memory. and again to continually bring the technologies to keep data centers Using the SFF-8630 connector (a superset of the SFF-8680 standard and give IT managers the ability to “Tame the Data Beast.”

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