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SAS enters the mainstream By the InfoStor staff http://www.infostor.com/articles/article_display.cfm?section=artcl&c=newst&article_id=295373&keywords=adaptec&p=23 Although adoption of Serial Attached SCSI (SAS) is still in the infancy stages, the next 12 months bode well for proponents of the relatively new disk drive/array interface. For example, in a recent InfoStor QuickVote reader poll, 27% of the respondents said SAS will account for the majority of their disk drive purchases over the next year, although Serial ATA (SATA) topped the list with 37% of the respondents, followed by Fibre Channel with 32%. Only 4% of the poll respondents cited the aging parallel SCSI interface (see figure). However, surveys of InfoStor s readers are skewed by the fact that almost half of our readers are in the channel (primarily VARs and systems/storage integrators), and the channel moves faster than end users in terms of adopting (or at least kicking the tires on) new technologies such as serial interfaces. Click here to enlarge image To get a more accurate view of the pace of adoption of serial interfaces such as SAS, consider market research predictions from firms such as Gartner and International Data Corp. (IDC). Yet even in those firms predictions, SAS is coming on surprisingly strong, mostly at the expense of its parallel SCSI predecessor. For example, Gartner predicts SAS disk drives will account for 16.4% of all multi-user drive shipments this year and will garner almost 45% of the overall market in 2009 (see figure on p. 18). IDC s disk-drive shipment projections underline the same general trend toward serial interfaces, but differ in the specifics. For example, IDC expects SAS to account for 15.7% of the enterprise drive category shipments this year, and almost 26% in 2009 (see figure on p. 18). However, regardless of which predictions prove to be more accurate, it s clear that SAS has hit the mainstream in a relatively short period of time. The basics

Unlike parallel transmission technology, which transmits data in multiple streams, serial interfaces send data in a single stream. As such, they are not tied to a particular clock speed and can send data faster. SAS, for example, has a theoretical maximum transfer rate of 3Gbps (in both directions), as does the current generation of SATA. The current generation of Fibre Channel has a maximum transfer rate of 4Gbps. SAS overcomes some of the inherent limitations of parallel SCSI, such as signal skew and crosstalk, signal termination restrictions, cable and connector reflection, lack of scalability and performance, and device addressability (theoretically, up to 128 devices with SAS, or more than 16,000 devices per domain with expanders, compared to only 15 devices with parallel SCSI). Although many of the advantages of SAS (versus parallel SCSI) relate to packaging issues that may be of more interest to OEMs and integrators (e.g., thinner cables, etc.), end users will be drawn to the speed advantages and what some think is SAS s crowning achievement: SAS enclosures can support both SAS and/or SATA disk drives. This capability gives users and integrators the ability to create tiered storage systems or domains that combine higher-performance SAS drives with higher-capacity (and lower-cost/ performance) SATA drives. Other benefits of SAS include dual-ported drives (also a feature of Fibre Channel drives), the use of expanders for adding external capacity, and a point- to-point connection architecture (vs. parallel SCSI s shared-bus architecture) for higher performance. In a point-to-point architecture, each device has a dedicated path to the controller, with full bandwidth on each connection. SAS also features multi-lane, or wide, connections so that, for example, an x4 (or 4x ) connection provides up to 24Gbps aggregate, bidirectional throughput. New products Market research firms predict a rosy future for SAS, but another way to gauge market momentum is by the number of product introductions. And there have been a slew of SAS products released recently. Here s a sampling of SAS products that went into production shipments over the last few months: Click here to enlarge image Accusys 64-bit ACS-93000 SAS-SAS RAID controller supports SATA native command queuing (NCQ) and SCSI tagged command queuing (TCQ), and has dual PCI-X connections, up to 16 SAS drive channels, a 533MHz RISC I/O processor, up to 4GB DDR2 cache memory, support for all RAID levels (and multiple RAID levels and stripe sizes in a single disk group), online disk group defragmentation and LUN capacity expansion, and support for Windows Virtual Disk Service (VDS) and Multi-Path I/O (MPIO). Adaptec is shipping five Unified Serial SAS/ SATA RAID controllers for PCIe systems. The low-profile cards are designed for entry-level to midrange servers and workstations. The controllers are available with four internal ports (model 3405), eight internal ports (model 3805), 12 internal ports (model 31205), 16 internal ports (model 31605), or eight external ports with dual-path fail-over (model 3085).

Click here to enlarge image Features include Performance: Hot Space (RAID-5EE) spreads the hot-spare disk space across the array and increases performance by using the spare spindle; Data protection: Dual-drive failure protection (RAID 6) ensures the array can survive two disk failures without losing data; and Management: Users can manage data backups by taking point-in-time snapshots (via an optional Snapshot Backup feature) and copying them to tape or disk without taking arrays offline. A hotspare slot can be designated in the disk cabinet, so after replacing a failed drive the array will reconstruct to its original configuration. Pricing for the controllers, which come with up to 256MB of cache and support for RAID arrays of up to 512TB, ranges from $390 to $995. Click here to enlarge image Advanced Industrial Computer s (AIC) Xtore division is shipping the XD 2000 RAID arrays, which support SAS/SATA drives and can be configured with dual 4Gbps Fibre Channel or 3Gbps x4 SAS host channels per blade. The XD 2000 includes RAID 50 Interleave (RAID 50i) for higher availability. RAID 50i creates multiple RAID-5 drive strata within a single RAID set across single or multiple enclosures within a storage domain, and protects against multiple drive failures. Xtore officials claim that RAID 50i does not have the overhead and performance penalties sometimes associated with RAID 6. The XD 2000 subsystems also support RAID 0, 1, 5, and 6. Other features include dual active controller blades, logical volume virtualized storage, and support for up to 16 drives in a 3U enclosure. Arena Maxtronic recently began shipments of the JanusRAID2 SS-6651E and SS-6652E RAID storage systems. The SS-6651E has a 4Gbps Fibre Channel host interface and the SS-6652E has a 3Gbps four-lane (x4) host interface that provides 12Gbps of aggregate throughput. Both subsystems support all RAID levels, including the company s NRAID, as well as JBOD configurations. Logical disks and volumes have independently configured stripe sizes, support online initialization, and sequential prioritized rebuilding. Up to three RAID alteration tasks can be performed online without bringing a subsystem offline. (Tasks include disk group expansion, defragmentation, logical disk expansion, RAID level migration, and stripe size migration.) Reliability features include disk scrubbing, disk self test, and disk cloning.

Atto Technology entered the SAS adapter market with the ExpressSAS R348 (internal) and R380 (external) RAID adapters. The company also launched a SAS Advantage channel program for VARs and integrators targeting high-throughput environments such as digital video. Atto officials attribute the adapters performance in part to the company s Advanced Data Streaming (ADS) technology and the use of Intel s 800MHz IOP348 I/O processors for PCIe hosts. The company claims a throughput rate of up to 903MBps in a RAID-5 configuration with 256KB transfers across 12 3.5-inch SAS drives, or 979MBps with 4MB transfers. Like all SAS adapters, the ExpressSAS cards support both 3Gbps SAS and SATA drives. In addition to supporting virtually all standard RAID levels, the adapters support Atto s DV RAID, which is designed to accelerate performance in streaming media applications such as high-definition (HD) digital video editing. The cards feature a native (as opposed to bridged) PCIe implementation with x8 PCIe-to-SAS/SATA interfaces and come in a low-profile form factor. The R348 has user-configurable internal port options with x4 Mini-SAS connectors (eight internal, or four internal and four external), and the R380 has eight external ports (two x4 Mini-SAS connectors). Other features of the ExpressSAS adapters include support for up to 32 physical drives and 128 logical drives, 256MB of ECC SDRAM, and support for Windows, Linux, and Mac OS X platforms. MSRP for the adapters is $1,095. Ciprico s RAIDCore RC5000 line of SAS/SATA controllers for Windows and Linux platforms leverage software-based RAID. Compatible with PCI-X and PCI Express hosts, the controllers are currently available in 8-port configurations, with 12- and 16-port versions due next month. The company claims more than 1.1GBps throughput with 16 SATA drives. Users can create virtual arrays of up to 32 drives. Eight-port controllers supporting RAID 5 are priced at $299, and RAID-0/1/10 versions are priced at $219. Dot Hill s 2730 Turbo RAID array, which is targeted primarily at OEMs and integrators, is up to 40% faster than the model 2730 due to a new processor. The company claims 1,154MBps sustained throughput and transfer rates of more than 124,000 I/Os per second. Based on Dot Hill s R/Evolution architecture and SimulCache technology (which leverages dual RAID controllers instead of conventional cache mirroring), the disk array has 12 drives per enclosure (expandable to 56) in any mix of SATA or SAS drives. The 2U systems come with four Fibre Channel host interfaces, with SAS and iscsi external interfaces due later this year. The 2730 also supports RAID-6 (dual-parity RAID). Adding to its line of Fibre Channel (FC) and FC/SAS controllers, Emulex has introduced its IOC 500S-a pure SAS ASIC designed for OEMs. The IOC 500S simultaneously supports target and initiator modes, is based on Intel s IOP34x processors, and is compatible with Emulex s Service Level Interface (SLI), which allows system builders to leverage driver-compatible designs across different applications and protocols. Other features of the IOC 500S include BlockGuard technology for data integrity, scalability up to 512 targets per chip, and eight SAS/SATA ports. Enhance Technology s most recent SAS subsystems include the eight-drive RS8 SS, 16-drive RS16 SS, and eight-drive T8 SS. Common features include support for virtually all RAID levels (including RAID 6), SAS/SATA interfaces, and dual SAS ports. The company claims performance of up to 500MBps for the T8 SS, 550MBps for the RS8 SS, and more than 850MBps for the RS16 SS. The subsystems include Qsan controllers and can be configured with SAS drives from Hitachi (UltraStar), Maxtor (Atlas 10k/15k), or Seagate (Cheetah). Excel Meridian Data recently began shipping the SecurStor Astra ES SAS/SATA, Astra SA SATA, and Astra SA iscsi subsystems. The 2U Astra ES supports SAS/SATA drives, active-active fail-over/fail-back RAID

controllers, up to four 12-bay JBOD modules for scalability up to 45TB, single or dual controllers, SAS or Fibre Channel host interfaces, virtually all RAID levels (RAID 0, 1, 1E, 3, 5, 6, 10, 50, and 60), and Multi-Path I/O (MPIO) software. Hitachi GST s flagship SAS disk drives are the 3.5-inch Ultrastar 15K300 and 2.5-inch Ultrastar C10K147. The 15K300 comes in capacities up to 300GB and has a disk rotation speed of 15,000rpm and a 16MB cache buffer. In addition to SAS, the Ultrastar 15K300 is available with 320MBps Ultra320 SCSI or 4Gbps Fibre Channel interfaces. The Ultrastar C10K147 small-form-factor (SFF) drive has a rotation rate of 10,000rpm, a 16MB buffer, and a capacity of up to 147GB. IBM is shipping a variety of LTO-4 tape drives and libraries with SAS as an optional interface (see IBM ships LTO-4, broadens encryption, p. 1). Over the last couple months, Infortrend has begun volume shipments of a number of SAS subsystems. The EonStor A08S-G2130 and A12S-G2130 are SAS-to-SATA subsystems with eight or twelve drives, respectively, for PCI-X systems. Built on the company s ASIC400 chip and a 600MHz PowerPC FL CPU, the 2U subsystems support all RAID levels and include two wide SAS ports for up to 24Gbps aggregate throughput. The EonStor S16F-R1430 subsystem supports SAS/SATA drives and 4Gbps Fibre Channel host connections. Features include dual RAID controllers with four Fibre Channel connections per controller, all RAID levels, sustained throughput of more than 800MBps in RAID-5 writes, multi-lane SAS expansion channels for connecting to the company s JBOD arrays, and support for up to 64 drives with one RAID system and three JBOD arrays. The EonStor S16S-J1000 is a SAS- to-sas JBOD array available in single- or dual-controller configurations, with two SAS ports per controller. By cascading units, the ES S16S-J1000 can support up to 64 SAS or SATA drives. Infortrend is also shipping the EonStor A16S-G2130 RAID subsystems, which have SAS host connections and SATA drive connections. The 3U SAS-SATA array includes 16 drive bays, two SAS channels (with 12Gbps per channel), and support for all RAID levels. Intel s Storage Server SSR212MC2 is a quad-core system with Xeon 5300 series CPUs. The rack-mount server can be configured in a number of ways, including as a NAS box, as a SAN array, or as an application server with direct- attached storage. The storage server can also be configured with a choice of SAS and/or SATA drives and can support 14 drives for capacities ranging from 3.6TB with 300GB SAS drives to 9TB using 750GB SATA drives. Intel s storage server is based on a 2U chassis from Xyratex. Pricing starts at $2,800 without a RAID controller, or $3,600 with Intel s SRCSAS144e RAID controller. JMR is shipping a number of SAS subsystems, some with PCIe host connections. The company s 3U Storage Server comes with dual Xeon processors and up to 16 3.5-inch SAS/SATA drives (for 16TB of capacity with SATA drives or 4.8TB with 15,000rpm SAS drives). The subsystems support PCI-X and PCIe expansions slots and come with a SAS JBOD or RAID controller. SATA JBOD or RAID controllers are optional. JMR is also shipping a 3U, 16-bay SAS-SATA JBOD expander unit with dual 4x SAS ports and up to 16 SAS or SATA drive connections.

In a twist on traditional host connections, JMR s PeSAN JBOD or RAID subsystems have a PCIe port for host connection and 16 SAS/SATA drive ports. Features are similar to the company s Storage Servers: 3U enclosure with 16TB of capacity with SATA drives or 4.8TB with SAS drives. Users and integrators can scale capacity by adding PCIe-based PeSAN External Switch units, PCIe x8 Extender Storage Systems, or PCIe internal-toexternal adapters. The latest members of LSI s SAS product lineup are the 4-port MegaRAID 8204 and 8-port MegaRAID 8208 adapters. Designed for low-end to midrange servers and workstations, the low-profile 8200 series adapters support SAS or SATA drives, RAID 5, and PCI-X or PCI-Express host buses. MSRP for the 4-port 8205 adapter is $229, and $315 for the 8-port MegaRAID 8208. In April, LSI announced that it had shipped more than two million SAS IC devices. NEC Corp. of America recently announced a wide range disk arrays that can be configured with SAS and/or SATA drives for scalability beyond 1PB. Promise Technology recently began shipping SAS products in its VTrak line of storage subsystems and SuperTrak line of RAID HBAs. The 2U, 12-drive VTrak E-Class disk arrays support SAS/SATA drives, 4Gbps Fibre Channel host connectivity (model E310f) or 3Gbps SAS host connectivity (model E310s), dual controllers, hardware-accelerated RAID 5/6, and the PCIe bus, and are based on Intel s IOP341 processor and XScale architecture. Promise s SAS RAID controllers on its SuperTrak EX series of HBAs are based on Intel s IOP348 processors and can be configured for internal or external connectivity. Seagate s 2.5-inch Savvio 15K SAS disk drive, which Hewlett-Packard uses in its ProLiant servers, has a rotation rate of 15,000rpm and a capacity of 36GB or 73GB. Versus 3.5-inch, 15,000rpm drives, Seagate claims the 2.5-inch Savvio 15K is 70% smaller and 1.12 pounds lighter, and uses 30% less power. Seagate specs the drives at a mean time between failure (MTBF) rate of 1.6 million hours. Xyratex has added to its line of nearline data storage systems with the F5404E FC-to-SAS/SATA RAID array. The F5404E has a fault-tolerant architecture with two RAID controllers per chassis and host-based dynamic multi-pathing that maintains continuous access to application data. Additional features include four 4Gbps Fibre Channel host connections, 3Gbps SAS/SATA drive connectivity, RAID 6, and snapshots. The system scales to 36TB in less than 4U of rack space. In addition, major server vendors such as Dell, Hewlett-Packard, and IBM are shipping servers with directattached SAS/ SATA drives. The only notable holdouts so far in the trend toward SAS are EMC and Network Appliance, which have not yet announced support for SAS. InfoStor June, 2007 Author(s) : InfoStor Staff