SAS Starts to ROC

RAID-on-a-chip controllers for SAS show chip makers' focus on serial interfaces

March 30, 2005

3 Min Read
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Led by Broadcom Corp. (Nasdaq: BRCM) and LSI Logic Corp. (NYSE: LSI), chip vendors are starting to deliver RAID-on-a-chip (ROC) controllers in time for the expected arrival of serial-attached SCSI (SAS) drives later this year (see Interoperability Lab Plugs SAS).

Broadcom demonstrated its first SAS ROC Feb. 28 at the Intel Corp. (Nasdaq: INTC) Developer Forum, and LSI Logic followed with a SAS ROC announcement last week (see Broadcom Offers SAS/SATA ROC and LSI Logic Stacks SAS ROC). Both have hopes of getting design wins with system OEMs that will show up in shipping products by the end of 2005.

Intel, Adaptec Inc. (Nasdaq: ADPT), Applied Micro Circuits Corp. (AMCC) (Nasdaq: AMCC), PMC-Sierra Inc. (Nasdaq: PMCS), and Vitesse Semiconductor Corp. (Nasdaq: VTSS) are likely to "ROC on" as well.

Though the ROC controllers are just coming out, there has been jockeying, by way of acquisitions and partnerships, in this space for years. It goes back at least to April 2003, when Intel and Emulex Corp. (NYSE: ELX) forged a joint development deal involving Intels low-power XScale processors to create controllers for Fibre Channel, SATA, and SAS (see Intel, Emulex Join at the Chip).

Other moves followed:

  • Broadcom acquired startup RaidCore for $16.5 million in February 2004, giving it the technology for ROC and RAID-on-a-motherboard (ROM) (see Broadcom Raids SATA Startup).

  • Last March, AMCC paid $150 million for SATA controller startup 3ware (see AMCC Buys More Storage).

  • In January 2005, Adaptec formed a partnership with Vitesse to develop SAS ASICs (see Adaptec Posts $3.5M Loss). The companies said they will combine Vitesse’s 6-Gbit/s mixed signaling technology with Adaptec’s RAID and I/O expertise. Adaptec has since released a SCSI ROC controller, but no SAS ROC yet.

The SAS ROC controllers will also support SATA drives. One analyst says the move from parallel to serial drive interfaces is a logical place for telecom chip vendors such as AMCC, Broadcom, PMC-Sierra, and Vitesse to make their marks in storage (see PMC Still Likes Storage, Chip Trio Faces Post-Bubble Blues, and Broadcom Raids SATA Startup). Those chipmakers already have expertise with serial interfaces.

“The serial technology in SATA and SAS is similar to what has been used in telecom for years,” says Sean Lavey, IDC program manager for semiconductor research. “Now SATA and SAS OEMs are interested in embedded solutions that would offload RAID processing.”

One of the biggest advantages of ROC designs is cost. Instead of integrating two pieces of silicon -- a RAID chip and protocol chip -- ROC requires only one. Broadcom storage marketing director Shriraj Gaglani estimates ROC can cut the price of two-chip controllers in half. ROC also reduces power consumption, and the Broadcom and LSI Logic designs allow either PCI Express or PCI-X host interfaces.

Size will also become more of an issue with a move to 2.5-inch drives for SAS and as blade severs gain in popularity. “Real estate is a big cost issue with the rise of blade servers. You can’t have multiple chips inside of a blade server,” Lavey says.

ROC is limited to servers for now. Broadcom’s Gaglani says he expects it to move into embedded storage arrays next year. That will probably happen first with SANs built for the SMB market.— Dave Raffo, Senior Editor, Byte and Switch

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