The need for speed: 6Gbps SAS and 8Gbps FC

Posted on September 01, 2009

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By the InfoStor staff

Switch and host bus adapter (HBA) vendors have been shipping 8Gbps Fibre Channel gear for some time, although disk arrays based on 8Gbps Fibre Channel are still scarce. That's also the case with 6Gbps SAS disk arrays, but in both cases a flurry of new product introductions is expected over the next couple months.

In the case of SAS, 6Gbps technology is expected to further fuel rapid adoption. Market researcher IDC expects SAS to account for half of all enterprise-class disk drive shipments this year, and almost three-fourths by 2012 (see Figure ).

Here's a quick rundown of some recent 6Gbps SAS and 8Gbps Fibre Channel product announcements in the disk drive, array and controller arenas.

6Gbps SAS

Hewlett-Packard became the first major systems/storage vendor to provide an end-to-end 6Gbps SAS infrastructure last month with the introduction of 6Gbps SAS disk drives, Smart Array RAID controllers, ProLiant G6 servers and, soon, the new D2000 family of 6Gbps SAS disk enclosures.

The 6Gbps SAS disk drives are available in 2.5-inch, 7,200rpm Midline versions, as well as 10,000rpm and 15,000rpm versions in capacities ranging from 72GB to 500GB. The drives are available for ProLiant models DL380, DL370, DL360 and DL180 servers, as well as the ProLiant BL460c server blade and ProLiant ML370 and ML350 tower servers.

HP's Smart Array RAID controllers include features such as online capacity expansion, mirror splitting and recombining, and online drive flashing.

LSI recently began shipping the first 6Gbps SAS controllers in its MegaRAID product line, which also support 3Gbps SATA drives, solid-state disk (SSD) drives, and self-encrypting drives (SEDs) in conjunction with LSI's SafeStore Encryption Services and controller-based key management.

The MegaRAID 9200 series includes 6Gbps SAS features such as self-discovery and self-configuring expanders, longer cables (up to 10 meters), standardized zoning, spread spectrum clocking, and decision feedback equalization (see Table, and for more information on 6Gbps SAS features, see "Market prepped for 6Gbps SAS" and "'Do more for less' with 6Gbps SAS" at infostor.com. Another good source for SAS information is the SCSI Trade Association: scsita.org.)

At the silicon level, 6Gbps SAS doubles the performance of 3Gbps, but LSI's MegaRAID 9200 offers more than 2X the performance of its 3Gbps predecessors due to improvements in firmware and drivers, according to Suresh Panikar, LSI's senior manager of worldwide marketing.

For example, LSI cites performance of more than 2,875MBps on reads (vs. a maximum of 1,200MBps for previous generation 3Gbps RAID controllers), more than 1,870MBps on writes (vs. 800MBps with 3Gbps controllers), and 200,000 I/Os per second (IOPS) per controller.

The MegaRAID 9200 series is available in five configurations:

  • 9260-4i (four internal ports, $389)
  • 9260-8i (eight internal ports, $599)
  • 9260DE-8i (eight internal ports with LSI's SafeStore encryption, $729)
  • 9280-8e (eight external ports, $859)
  • 9280DE-8e (eight external ports with SafeStore, $945)

The RAID controllers are based on the LSISAS2108 RAID-On-Chip (ROC), 512MB of 800MHz DDR2 SDRAM, and an x8 PCI Express 2.0 host interface. The cards are shipping to LSI's channel partners.

Earlier this year, LSI demonstrated more than one million IOPS on a single server powered by three LSISAS2108 RAID chips connected to 12 2.5-inch 6Gbps SAS drives.

LSI has 6Gbps SAS design wins with vendors such as Dell, Fujitsu Siemens, IBM, Intel, NEC, Sun and Supermicro.

Seagate last month began shipping to the channel 3.5-inch Cheetah 15K.7 drives, which are available with either 6Gbps SAS or 4Gbps Fibre Channel interfaces. Maximum capacity of the drives is 600GB.

The Cheetah 15K.7 drives include Seagate's PowerTrim technology, which reduces power consumption. This month, Seagate added optional Self-Encrypting Drive (SED) technology for security-conscious users.

Hitachi Global Storage Technologies (GST) is shipping dual-port, 10,000rpm, 6Gbps SAS drives. The C10K300 drives come in 147GB or 300GB capacities, and have Advanced Power Management technology for lower power consumption (3.4 watts in idle mode, and 6.1 watts in active mode). Average seek time is 3.9 milliseconds, and average latency time is 3 milliseconds.

Promise Technology is expected to officially announce its 6Gbps SAS controllers in the October-November time frame. Two models will be available: the SuperTrak EX8760T (with eight internal SAS/SATA ports and 256 or 512MB of ECC DDR II memory) and the EX8768 (eight external ports and 512MB of memory).

Common features of Promise's 6Gbps SAS RAID controllers include PMC Sierra's 500MHz 8011 I/O processors, hardware-accelerated RAID (including RAID 6) and support for 32 logical drives per array and 256 arrays per controller.

On the performance front, in internal tests with 24 drives in pass-thru mode with 512-byte blocks, Promise claims 180,000 IOPS on sequential reads and writes, 8,000 IOPS on random reads and writes, and throughput of 2,000MBps with 256KB blocks. In a RAID-5 configuration on the same test bed, the company clocked 130,000 IOPS with 512-byte blocks on sequential reads, 120,000 IOPS on sequential writes, 130,000 IOPS on random reads, 2,000 IOPS on random writes, and throughput of 1,700MBps on sequential reads and 1,300MBps on sequential writes with 256KB blocks.

NEC is integrating Promise's SuperTrak 6Gbps SAS RAID controllers, with 8x PCIe 2.0 host bus interfaces, into its next generation servers.

Last month, Promise began shipping the VessRAID series of RAID subsystems with SAS/SATA drive connections and SAS or iSCSI host connections. The arrays are available in a 2U chassis with up to 12 drives or in 3U versions with up to 16 drives. Users can add as many as four additional chassis for a total of 60 drives (2U) or 80 drives (3U). The VessRAID arrays come with 512MB of cache (upgradeable to 2GB).

In a RAID-5 configuration, Promise claims a maximum read throughput rate of about 936MBps and a write rate of 728MBps with SAS drives, and a maximum read rate of 764MBps and 669MBps on writes using SATA drives.

Atto Technology is shipping five 6Gbps SAS host adapters in its ExpressSAS family: the H608 (eight internal ports), H680 (eight external ports), H644 (four internal and four external ports) and, most recently, the H60F (16 internal ports) and H6F0 (16 external ports), both of which have dual independent controllers. Other features include x8 PCIe 2.0 support and Atto's Advanced Data Streaming (ADS) technology for bandwidth-intensive applications.

Atto has also added support for 6Gbps SAS host connections on its FastStream Storage Controller. The FastStream SC 8200 RAID controller supports 4KB sector sizes to address partitions larger than 2TB. In addition to 6Gbps SAS, the controller supports 8Gbps Fibre Channel host interfaces.

For testing 6Gbps SAS gear, JDS Uniphase (which acquired Finisar's Network Tools group earlier this year) is shipping the Xgig 6Gbps SAS Target Emulator, a test and analysis platform that also works with 3Gbps and 1.5Gbps devices. The emulator supports bi-directional SAS target emulation up to level-4 functionality (e.g., SCSI and ATA commands) and has compare circuitry to verify accuracy without, according to the company, imposing performance penalties. Dual wide-link connector blades support four SAS lanes per connector, or up to eight lanes per chassis.

Aimed primarily at storage equipment designers, testers and manufacturers, the Xgig Target Emulator supports up to 32 synchronized ports cascaded across multiple chassis (in a single "sync group"), and up to 32 simultaneous users. Other features include support for the SATA Tunneling Protocol (STP), hardware-based encryption, and automated operation.

The Xgig Target Emulator can be used with the Xgig Analyzer (to capture and analyze traffic), Xgig Generator (for creating arbitrary traffic), and Xgig Jammer (to modify live traffic). The Target Emulator is part of the company's Monitoring and Analysis platform.

JDS Uniphase also has a full line of test equipment for 8Gbps Fibre Channel.

And on the solid-state disk (SSD) front, STEC plans to deliver by the end of the year a version of its ZeusIOPS SSDs with 6Gbps SAS interfaces. The company claims performance of 80,000 IOPS with random read operations, 40,000 IOPS on random writes, and transfer rates of 550MBps on reads and 300MBps on writes. The 6Gbps SAS SSDs will be available in 2.5-inch and 3.5-inch form factors, and will support single-level cell (SLC) and multi-level cell (MLC) flash technology.

8Gbps Fibre Channel arrays

LSI's most recent 8Gbps Fibre Channel RAID array is the mid-range Engenio 4900, which was introduced at the end of last month and includes 8Gbps Fibre Channel or, optionally, 1Gbps iSCSI host interfaces.

The Engenio 4900 comes with four 8Gbps Fibre Channel host connections, with the option of adding four additional 8Gbps Fibre Channel connections or four iSCSI interfaces. The arrays also have four 4Gbps Fibre Channel drive expansion connections.

The disk array can support up to 112 drives (Fibre Channel and/or SATA), for a maximum capacity of 50TB with 450GB Fibre Channel drives or 112TB with 1TB SATA drives.

In terms of performance, LSI cites a maximum burst I/O rate from cache of 200,000 IOPS, a maximum sustained I/O rate from the disk of 50,000 IOPS, and a maximum sustained transfer rate from the media of 1,600MBps.

Functionality available with LSI's SANtricity Storage Manager software includes snapshots, volume copy and remote volume mirror. All RAID levels are supported, including dual-parity RAID 6. Another feature is SafeStore encryption services, which combine key management and drive-level encryption for security.

LSI also supports 8Gbps host connectivity on its higher-end Engenio 7900, which has 16 8Gbps or 4Gbps Fibre Channel host connections and up to 448 Fibre Channel or SATA drives, for a total capacity of 448TB with 1TB SATA drives.

Last month, Infortrend introduced two disk arrays with 8Gbps Fibre Channel host connections in its Enterprise Scalable Virtualized Architecture (ESVA) family: the F20 (with SATA drives) and the F60 (with SAS drives). Both 3U arrays have replication and snapshot functionality, up to 112 drives (via JBOD), four 8Gbps Fibre Channel host ports, and 8GB of cache memory.

The ESVA-F20 has a starting capacity of 16TB and can be configured with up to 16 3.5-inch 7,200rpm SATA drives for a maximum capacity of 112TB (via JBOD). The ESVA-F60 has starting capacities of 2.4TB, 4.8TB or 7.2TB, and can be configured with up to 16 15,000rpm SAS drives and a maximum capacity of 50.4TB (via JBOD).

Rorke Data, a subsidiary of Bell Micro, is shipping the Galaxy Aurora LS array, which has one, two, four or eight 8Gbps Fibre Channel ports. The company claims MSRP pricing starting at less than $0.70 per MB. The array is targeted primarily at the video post-production market.

Rorke claims performance in excess of 1,000MBps on the Aurora LS, which has 16TB of capacity in a RAID-0 configuration or 13TB in a RAID-6 dual-parity configuration, and 6GB to 24GB of cache. The array supports multiple DV, SD, and uncompressed HD streams, as well as 2K streams.

Part of its OneStor Extensible Storage Platform family, Xyratex's F6500E RAID arrays have 8Gbps Fibre Channel host interfaces and up to 12 drives in a 2U form factor (expandable up to 96 drives), and can be configured with SAS or SATA drives. Xyratex sells primarily to OEMs.


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