By Dave Simpson
In a recent online poll of InfoStor readers (including end users, VARs, and systems/storage integrators), 43% said that SATA drives will account for the majority of their disk drive purchases over the next six months, and 28% cited Fibre Channel drives. Somewhat surprisingly, 25% said that SAS drives will account for the majority of their drive purchases. Not bad for an interface that has only been around for about two years.
Disk drive market predictions from research firms paint an even rosier picture for SAS. For example, IDC, which bases its estimates on data and projections from the disk drive manufacturers, expects SAS to account for almost half (48%) of all enterprise drive shipments this year, up from 35% last year. And IDC expects SAS to garner a commanding 70% market share by 2011.
Of course, SAS has a number of inherent advantages: It's the heir apparent to parallel SCSI, and SAS systems support both high-performance SAS drives as well as low-cost, high-capacity SATA drives, allowing users and integrators to mix-and-match "best of breed" devices and create "in-the-box" tiered storage (although that capability is hyped in marketing material more than it's deployed in actual end-user scenarios).
Increased adoption of SAS drives and subsystems is attributable to a number of other factors as well, including the following:
--Although hindered in the beginning by relatively high prices and low capacities (73GB and 147GB), a number of disk drive manufacturers have begun shipping 300GB, 500GB, and 750GB drives, albeit in limited quantities and at relatively high prices. And Seagate has begun shipments of 1TB SAS drives (the Barracuda ES.2 series);
--Due to the popularity of blade servers, one trend that is expected to create a surge in SAS drive shipments is the use of SAS as a fabric in blade configurations, as well as in rack enclosures;
--Although relatively few users/integrators actually mix SAS and SATA drives in SAS subsystems, the trend to do so will pick up, because vendors have solved issues such as vibration problems. "Not many users are mixing drive types in the same enclosure today, but there is a lot of interest in doing it," says Mike Karp, a senior analyst with Enterprise Management Associates (EMA);
--First-generation SAS drives have data-transfer rates of 3Gbps, but some manufacturers -- such as LSI -- are already shipping 6Gbps components. And 6Gbps SAS will offer a number of new features (see box). In addition, the SAS road map extends to 12Gbps transfer rates;
--Early SAS adapters had a relatively low number of ports, but vendors such as Adaptec are shipping SAS adapters with as many as 28 ports (see below for information on recent SAS product announcements); and
--The trend is away from 3.5-inch SAS drives to 2.5-inch small-form-factor (SFF) drives, which provide better power efficiencies and space savings.
As an example of the trend toward 2.5-inch SFF drives, in the first quarter of this year, SAS drives represented approximately two-thirds of Fujitsu's enterprise-level disk drive shipments, and 2.5-inch SFF SAS drives comprised approximately one-third of those shipments. For Fujitsu, SFF SAS drive shipments have grown more than 570% since early 2006. And industry analysts expect 3.5-inch SAS drive shipments to flatten out this year.
Shipments of SAS-based arrays, controllers and adapters have picked up significantly this year. Here's a sampling of just some of the recent product introductions, with an emphasis on products designed primarily for the channel.
Adaptec's Series 5 Unified Serial family of SAS/SATA RAID controllers have up to 28 ports (24 internal and four external ports) and are available in seven different configurations (starting with four internal ports). In a high-end configuration, users, integrators, or OEMs can attach up to 256 SAS or SATA drives to build systems with approximately 200TB of capacity.
The PCIe interface controllers are based on 1.2GHz Intel IOP348 I/O processors and XScale technology. MSRP ranges from $425 for a model 5405 with four internal ports to $1,595 for a model 52445 with 24 internal and four external ports. All of the controllers come with Adaptec Storage Manager (ASM) software.
Adaptec recently began shipping the entry-level Series 2 Unified Serial RAID controllers, which have the same dual-core RAID-on-Chip (ROC) architecture used in the company's Series 5 controllers. The Series 2 controllers support SAS and/or SATA drives and hardware-based RAID-0, -1, and -10 configurations. Adaptec claims compatibility with more than 300 SATA/SAS devices, including mid-planes, disk drives, and tape drives. The controllers are compatible with Linux 2.4.2 or later drivers.
The Series 2 PCIe RAID controllers come with 128MB of DDR2 cache and enable users and integrators to connect up to 128 SATA or SAS I/O devices using SAS expanders.
The family includes three products: the RAID 2405 Kit ($250) with four internal ports; the model 2405 Single ($225) with four internal ports; and the model 2045 Single ($250). The Series 2 cards come with the ASM management software.
Advanced Industrial Computer (AIC) recently introduced the MiniBOD XJ-SA01-08-A1 -- a portable device with eight 2.5-inch SFF SAS or SATA drives. The company claims a bandwidth of up to 2.4GBps and a capacity of up to 1.2TB. The device plugs into hosts via an SFF8088 connector.
Shipments of the eight-drive configuration began a few months ago. Planned enhancements, due later this year, include embedded RAID functionality on the backplane and configurations with four 3.5-inch drives. At the NAB show earlier this year, AIC demonstrated the MiniBOD system with Savvio SAS drives from Seagate and R380 series RAID controllers from Atto Technology.
Atto's most recent products in the SAS space are its 16-port ExpressSAS H30F adapters, which support both SAS and SATA drives. The H30F adapters have four internal (x4) MiniSAS SFF-8087 connectors for support of up to 256 devices via SAS expanders. The adapters combine x8 PCIe host bus technology and Atto's proprietary Advanced Data Streaming (ADS) technology for high-speed applications.
Due later this summer, Atto's 16-port, half-height ExpressSAS R30F adapters will add RAID functionality to the ExpressSAS line, including RAID 0, 1, 4, 5, 10, and 50 and Atto's DVRAID technology. Future versions will support RAID 6 (dual parity) and 60.
The latest addition to AMCC's SAS RAID controller lineup is the 3ware 9690SA-4I, which has four internal ports and is priced at an MSRP of $395. The controller is designed primarily for 1U, four-bay servers in direct-attached storage (DAS) configurations. AMCC is also shipping SAS RAID controllers with eight internal ports, eight external ports, and a version with four internal ports and four external ports. The 9690SA-8I, 9690SA-8E, and 9690SA-4I4E carry an MSRP of $795.
Arena Maxtronic is shipping FC-SAS and SAS-SAS RAID systems. The 4U, 24-bay JanusRAID2 SS-8811R and rack-mount SS-8812R support 4Gbps Fibre Channel-to-SAS connectivity or SAS-to-SAS connectivity.
Features of the Janus RAID arrays include an IOP 348 dual-core processor, active-active controllers, a SAS expansion port for connecting up to 120 disk drives, support for virtually all RAID levels (and multiple RAID levels and stripe sizes per disk group), and support for Windows VDS and MPIO.
Dot Hill recently entered the SAS market with the model 2530 RAID array, which includes two SAS interfaces per controller and connects to SAS or SATA disk drives. The controllers have 1GB of mirrored cache.
Based on Dot Hill's R/Evolution architecture, the 2U, 12-drive 2530 supports up to 56 SAS/SATA drives, with capacity scaling from 1.7TB to 56TB. Data-protection services include AssuredSnap snapshots (16 standard, 64 optional) and AssuredCopy volume copy capability. High-availability features include active-active controllers and support for MPIO. A SimulCache feature leverages redundant controllers and, according to the company, eliminates the performance degradation typically associated with conventional cache mirroring.
Enhance Technology's latest entries in the SAS space include the EnhanceRACK R4 and R8 Mini-SAS (MS) storage arrays. Compatible with both SAS and SATA drives/controllers/adapters, the systems come with Mini-SAS SFF8088 connections and have been tested with controllers/adapters from vendors such as Areca, Atto, HighPoint, and LSI.
The R4 MS is a 1U, four-drive enclosure, and the R8 MS is a 2U, eight-drive system with a data-transfer rate of 550MBps in a RAID-0 configuration, or 400MBps in a RAID-5 configuration.
Infortrend Technology is shipping iSCSI-to-SAS/SATA external RAID subsystems with four Gigabit Ethernet ports per controller. The single-controller EonStor (ES) S16E-G1130 and dual-controller ES S16E-R1130 are 3U, 16-bay arrays.
The arrays combine multiple host channels into a port group for increased performance. In a RAID-5 configuration with two host channels in a portal group, the S16E can achieve 215MBps on reads and 201MBps on writes, according to the company. With four host channels combined, the systems can hit 380MBps on reads and 250MBps on writes.
The systems can scale up to 80TB (with 1TB SATA drives) with expansion units. Each controller has one SAS expansion port for connecting to Infortrend's JBOD expansion units. Configurations include both RAID 5 and RAID 6.
iStor Networks is shipping its integraStor iS512 iSCSI arrays equipped with Seagate's new 1TB Barracuda ES.2 SS-series SAS drives. The iSCSI arrays can also be configured with SATA drives and/or lower-capacity, higher-performance SAS drives. The native interface on the new SAS drives eliminates the need for interposers, which reduces costs and complexity.
Seagate's 1TB Barracuda ES.2 drives include a PowerTrim feature that dynamically manages drive power consumption. Other features include a 7,200rpm rotation rate, an average seek time of 8.5ms, and a mean time between failure (MTBF) rating of 1.2 million hours.
Early this year, LSI introduced three half-length, low-profile MegaRAID SAS/SATA adapters based on the company's SAS1078 RAID on Chip (ROC), which come in a PCI Express MD2 form factor. The adapters range from four to eight internal ports, to eight external SAS/SATA ports.
In March, LSI began shipping to OEMs 6Gbps SAS expander ICs. The company also demonstrated a 6Gbps SAS infrastructure with partners Dell and Seagate. The demonstration included a Dell prototype server, Seagate disk drives, and LSI's ROC controllers and 6Gbps SAS expanders.
Finisar's Xgig Jammer 2.9 is a 6Gbps SAS error injector designed for protocol testing of storage subsystems. The device can be used for interoperability and compliance testing. In addition to SAS, the Xgig Jammer supports SATA, 8Gbps Fibre Channel, 10Gbps Ethernet, and iSCSI.
Promise Technology is shipping the SuperTrak EX8658 and EX8654 -- the latest additions to the company's host-based SAS/SATA RAID controllers. SuperTrak subsystems can be linked to Promise's 12-bay and 16-bay E-Class JBOD expansion units.
The SuperTrak EX8658 has eight external SAS/SATA ports, while the EX8654 has four internal and four external SAS/SATA ports. (Promise also sells the SuperTrak EX8650, with eight internal ports, and the EX4650, which has four internal SAS/SATA ports.) The RAID controllers come in a low-profile MD2 form factor.
RAID Inc.'s Razor is a 1U RAID array with Fibre Channel host connections and support for SAS/SATA drives. The array can be expanded in 1U increments up to 60 drives, including 2.5-inch, 15,000rpm SFF SAS drives. The Razor subsystems can be configured with up to 12 2.5-inch drives per enclosure and can be expanded with as many as four JBOD enclosures.
Razor arrays come with RAID Inc.'s StorageWatch service, which proactively monitors conditions such as irregularities in components, including controllers, drives, power supplies, cooling units, switches, backup devices, and the overall array.
Sans Digital's SAS lineup includes the EliteSTOR and EliteRAID series. The company recently began shipments of the 2U 12-bay EliteRAID ER212X, 3U 16-bay ER316X and 4U 24-bay ER424X, each of which includes a Mini SAS 4x connector for JBOD capacity expansion. Common features include an 800MHz Intel IOP341 I/O processor, support for virtually all RAID levels, dual Mini SAS host channels, PCI-X and eight-lane PCI-Express compatibility, and more than 12GBps internal bandwidth.
Sans Digital is also shipping the 1U EliteSTOR ES104 JBOD arrays, which support four 3.5-inch SAS or SATA drives for a maximum capacity of 4TB. Host interfaces include SAS, SATA, and InfiniBand.
Xyratex's OneStor SP1224 is the latest member of the company's OneStor Extensible Storage Platform (ESP) arrays. Designed primarily for OEMs, the array is a 2U, 24-drive subsystem with 2.5-inch SFF drives (Seagate's 10,000rpm or 15,000rpm Savvio devices) that is compatible with the Storage Bridge Bay (SBB) 2.0 specification. The arrays come with Xyratex's Intelligent Platform Manager (IPM) software, which provides self-healing, fault diagnosis and resolution capabilities, persistent error logging, and system status monitoring.
For more information on SAS and SATA . . .
SCSI Trade Association (STA)
Serial Storage Wire newsletter
SAS Resource Center (a sponsored "micro site")
T10 Technical Committee (SAS spec development)
Serial ATA-IO Organization
T13 Technical Committee (ATA spec development)
Nexsan ships SAS array with MAID
Nexsan Technologies recently began shipping the SASBoy RAID array, which features the company's AutoMAID (massive array of idle disks) technology. AutoMAID is an energy-saving technology that enables users to select between two settings to conserve drive-related energy while, according to the company, not affecting performance.
The 3U, 14-bay SASBoy can be configured with 15,000rpm, 300GB SAS drives for a total capacity of up to 4.2TB. (The controllers also support SATA drives, although Nexsan is not currently shipping mixed-drive configurations. Systems with 450GB SAS drives are expected within the next couple of months.)
The subsystems come with two 4Gbps Fibre Channel ports and two iSCSI/Ethernet ports per controller, and users/integrators can configure the systems with one or two (active-active) RAID controllers in RAID 0, 1, 1+0, 4, 5, and 6 levels.
Nexsan claims a sustained data-transfer rate of up to 875MBps, and 2,500 I/Os per second in a RAID-5 configuration with 4KB data transfers. (The IOPS rating is at the system level -- e.g., not from cache.)
The SASBoy supports as many as 255 LUNs. The controllers come with up to 2GB of cache, and the systems include the company's NexScan monitoring and management software. Pricing starts at $6,800 per terabyte.
What's in 6Gbps SAS
Implemented in accordance with SAS-2 spec
--Double transfer rate to 6GBps
--Up to 10m cable lengths
Standardized expander zoning
--Enhanced multi-host support
--Already available on some 3Gbps SAS expanders
Spread spectrum clocking
--Increases link efficiency/bandwidth over today's rate matching
--Investment preservation for today's infrastructure
Source: SCSI Trade Association