September 21, 2004

How GNU/Linux and Serial ATA RAID teamed up to save money

Author: Jem Matzan

Recently Mailroute, a company that provides virus and spam filtering for businesses, switched its GNU/Linux-based servers from SCSI to Serial ATA disks and saved itself a lot of money. The switchover wouldn't have been possible without Broadcom's new SATA RAID (Redundant Array of Inexpensive Disks) controller, the RAIDCore BC4852.

While the product was in development, RAIDCore was an independent company working with Mailroute as it developed a GNU/Linux product. When chipmaker Broadcom acquired RAIDCore earlier this year, there were some concerns that Linux support would get lost in the shuffle. Did one privately held company have enough sway to get Linux drivers and software support from Broadcom? "I'd like to think so," Mailroute CEO Thomas Johnson told NewsForge.

On Monday, Broadcom officially announced the release of its new BC4852 RAID controller, but Mailroute has been beta testing the product for some time. This product reputedly offers the same high performance and large number of disks as competing SATA RAID products from 3ware and others at a substantially lower price. But, just as GNU/Linux is overtaking proprietary Unix installations, SATA RAID is beginning to overtake SCSI RAID in production environments.

Johnson and his engineers originally tested the RAIDCore card on Windows-based machines, since the hardware didn't have drivers for other operating systems. But since they didn't use Windows in their production environment, the product was useless to them. So Johnson called RAIDCore and told them that he liked the hardware but needed software and drivers that would work with GNU/Linux -- specifically Red Hat 9. RAIDCore engineers began development of Linux drivers and software, and Broadcom allowed them to continue their work.

"We've got IBM xSeries 235 and 335 systems, one's a tower and one's a 1U rackmount box. We asked IBM if they could add a hot-swappable SATA backplane, and they couldn't help us. So we ripped out their SCSI backplane and put our SATA drives in," Johnson said. The small 1U rackmount form factor also requires half-height peripheral cards; not only is the Broadcom RAIDCore BC4852 a half-height card, but it comes with rear faceplates for both half and full-height chassis.

Why SATA RAID?

Serial ATA is the connection standard of the future for hard drives. Standards come and go as technology advances, but for the next few years, if you want a quality, inexpensive hard drive, it's going to have to be SATA. The only real difference between SATA and SCSI or parallel ATA is the electronics and the connection standards; the mechanical components of the drives are the same.

Traditionally, SCSI has been the standard for mission-critical systems in production environments; it offers outstanding performance and high reliability at a premium cost. Usually you'll find production servers running RAID to enhance system speed, reliability, and storage space. There are many different RAID modes, but RAID-5, which combines three or more disks to increase storage space while simultaneously offering redundant data protection, is the most popular.

The RAID controller takes the drives connected to it and manipulates them to your preference. If you have a number of identical hard drives, you can consolidate their space and efficiency by putting them into an array via a RAID BIOS, which is much like your computer's BIOS except it only affects the RAID controller. When the system gets past its power-on self test, the RAID is seen by the system as one disk, assuming you have the proper driver for your operating system. Some controllers, like the ones built into Intel motherboards, will allow you to simply connect a drive and use it standalone without having to go through the RAID BIOS.

The BC4852 requires Broadcom's proprietary software to take advantage of its most interesting features, and the Linux drivers are also closed-source -- for the time being, at least. A Broadcom representative told NewsForge on Monday that the drivers would be open sourced in 1Q 2005. That's good news for their customers -- especially Mailroute.

"I'd really like to see the Broadcom driver in the Linux kernel," Johnson said. "When I can get the driver through the default installation, the product gets a bigger vote of confidence from me than when we have to get drivers from a third party."

"We had such a large call for Linux support that we decided to engineer Linux drivers," Jeff Huber, a Broadcom representative told us last week. The Broadcom drivers were not ported or adapted; they were written specifically for GNU/Linux. According to Huber, only the Windows edition of the controller software has a graphical user interface; the GNU/Linux edition is controlled through the command line interface.

Currently the RAIDCore BC4852 drivers and software only support Red Hat Linux 9, Red Hat Enterprise Linux 3, and Fedora Core 1.

Broadcom sent us a controller to review, but the driver installation procedure involved using a diskette, which this reviewer has not had or needed in several years. Broadcom rushed to get us an ISO so that we could use a CD instead, but as of Monday afternoon we still couldn't get it to work properly on Red Hat 9 or Red Hat Desktop. Broadcom is, however, working to resolve the issues and hopes to offer tested and qualified ISO images as an alternative to diskettes.

Jem Matzan is the author of three books, a freelance journalist and the editor-in-chief of The Jem Report.

Category:

  • Storage
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