RAM | Reseller Advocate Magazine: Issue 53

By Chris Angelini


	Integrated RAID Don’t confuse desktop RAID technology for enterprise hardware. NVIDIA’s nForce4 SLI chipset supports heavy-duty RAID 5, but it’s best suited to powerful graphics workstations.

If a customer were to ask you how an HBA differed from a RAID controller, what would you say? Could you explain the differences between cards with hardware I/O processors and those reliant on software? Don't sweat it if you're a little fuzzy on the intricacies of today's disk controller landscape. As SATA and SAS blur the once well-defined line between enterprise and mainstream, it's getting harder to be specific on the technology and easier to just let price do the talking.

Should We Blame Integration?

You could argue that integration is causing core logic to look more and more like high-end hardware. After all, even your desktop motherboards with Intel ICH7-R southbridges include advanced RAID features. Much of NVIDIA's nForce4 lineup is equipped with very similar functionality. So why would your customer want to pay an extra $400 for an add-in disk controller when they can get many of the same features free of charge?

First things first. It's important that your customer understands where an integrated solution works well and where it comes up short.

"It takes chipset vendors much longer to integrate enterprise storage technologies into motherboards, so you might already be obsolete by the time a new feature is enabled," says Jim Evans, product marketing manager for LSI Logic's Engenio storage group. "Take SAS, for example. We already know that there is an effort to add SAS 3 Gbps to server core logic. However, by the time it actually happens, SAS 6 Gbps should be right around the corner."

Of course, SAS is a higher-end disk interface less sensitive to price than the dominant desktop standard, SATA. That desktop market is where integration is your ally. A motherboard with an Intel ICH7-R hub will sport at least four SATA ports, each accommodating the newest 3 Gbps hard drives. Moreover, Intel's Matrix Storage Manager software extends support for RAID 0, 1, 5, and 10 modes.

There's actually a lot to like about the current crop of RAID-capable chipsets as they pertain to desktop and workstation computing. Intel's ICH7-R sports a built-in BIOS ROM to enable convenient pre-OS array configuration. NCQ (native command queuing) and hot-swap are also standard value-adds. In the same vein, NVIDIA's nForce4 SLI chipset boasts bootable RAID 5, hot-spares, and RAID configurations that span SATA and legacy PATA hard drives, too. In all, those chipsets include a nice list of traditionally high-end features many enthusiasts can appreciate.

Unfortunately, most server platforms are missing such built-in extras. On the Intel side, nearly all Xeon boards employ older communications hub technology—either the ICH5-R or ICH6-R, limited to RAID 0 and 1. Many AMD Opteron platforms fare a little better thanks to NVIDIA's nForce Professional chipset, which wields SATA 3 Gbps compatibility. However, RAID 5 is still consistently absent. Only when you drop down to entry-level Pentium- and Athlon-based workstation products do those features appear.


	Quick and Easy SAS When you just need to enable SAS connectivity, whether to drives on a backplane or an external enclosure, LSI Logic's SAS3442X HBA is a cost-effective solution.

Introducing the HBA

Consequently, it's often best to equip servers and true workstations with industrial strength disk controller technology. But how do you pick the right card? Start by understanding the difference between an HBA (host bus adapter) and a RAID controller.

According to Paul Vogt, director of product marketing for Adaptec, an HBA is a general connectivity device that, when it does offer RAID support, utilizes a system's CPU for the necessary processing.

"A RAID controller, on the other hand, offers three primary benefits: it offloads RAID functionality to an I/O processor, it is operating system independent, and it is often much more feature-rich."

Granted, both classes of hardware have their pluses and minuses. If you think back a few months, HBAs were the first devices enabling SAS disk support right out of the gate. In fact, LSI Logic's SAS3442X accompanied the first pre-production Seagate SAS drive we ever tested, long before onboard ASICs or RAID controllers were ready for prime time.


	Massive Storage Muscle Adaptec's RAID 4805SAS card has enough processing power for advanced RAID levels like 5, 6, 50, and 60.

Because they're less complex, HBAs are usually much more affordable than RAID controllers. Compare the same eight-port SAS3442X to LSI's like-sized MegaRAID SAS 8408E and you'll see a doubling of price. Both accommodate the same number of devices, and certain variants of the HBA even support RAID 0, 1, 1E, and 10E.

"The HBA might even outperform a RAID controller in some situations," says LSI's Jim Evans, "especially since you're processing on a super-fast host processor using system memory. Of course, as loading increases, the performance of an HBA will dip. We regularly see 30% to 60% host CPU utilization on an HBA versus 7% or less with dedicated hardware."


	Drop-In Hardware RAID Supermicro's LPZCR2 Zero-Channel RAID card is a perfect upgrade for customers graduating from an onboard HBA. It supports 17 different Supermicro motherboards, simplifying inventory, too.

In the Other Corner, RAID

Meanwhile, RAID controllers sport their own list of reseller-friendly features sure to whet the palates of power-hungry customers.

"Scalability is an issue that hardware RAID controllers readily address," says Adaptec's Paul Vogt. "As you add one, two, or three cards, dedicated I/O processors keep the server from getting bogged down."

OS independence is another VAR favorite proffered by RAID hardware.

"Adaptec makes the setup process easy by exposing all functionality to the user before they even load an OS." says Vogt. "Drivers and management software are provided after-the-fact, of course, but the comprehensive configuration utility guarantees your operating system will recognize whatever RAID array you define."


	Small Business RAID Want the benefits of hardware RAID without the prohibitive price tag? HighPoint's eight-port RocketRAID 2320 does RAID 0, 1, 5, 10, and 50, all for less than $300.

Then there's the issue of functionality. An onboard I/O processor (complementing the I/O controller) paves the way for more intensive operations. That's why you'll find many RAID cards with extensive array support. Adaptec's Serial Attached SCSI RAID 4805SAS, for instance, works with RAID 0, 1, 5, 10, and 50. An optional upgrade to the Advanced Data Protection software suite adds RAID 1E, 5EE, 6, and 60 as well.

Customers who simply cannot afford to compromise information will likely peg the potential data integrity advantages of hardware RAID. In the unfortunate event of a power failure, a RAID controller with battery backup preserves any data in the I/O processor's cache memory, ensuring that it's written to disk whenever power is restored.

Do Your Homework

As Adaptec and LSI Logic tailor flexible HBAs and RAID controllers in PCI Express and PCI-X trim, their partners innovate alongside them. Motherboard vendor Supermicro is a perfect example. Its X6DH3-G2 server board features Adaptec's AIC9410 eight-port SAS controller—an onboard HBA, in essence. However, if your customer decides to upgrade down the road, you can drop a proprietary zero-channel RAID card into an available PCI-X slot and add a 600 MHz Intel I/O storage processor, 256MB of cache, and a host of hardware RAID features. Such a product could give you an edge up on small businesses expecting rapid near-term growth.


	Upgrade with ROMB Customers looking for more from their SE7520JR2 motherboard can upgrade to hardware Ultra320 RAID with a special activation key from Intel.

Intel sells a similar idea, only its boards, the pedestal-ready SE7520JR2 and rackmount SE7520AF2, are still touting Ultra320 SCSI. A special ROMB (RAID on motherboard) activation key available at distribution unlocks similar hardware functionality, complete with up to 1GB of cache memory.

According to Robert Stoddard, team lead for RAID technical marketing at Intel, the company will be moving to SAS in a big way as its much-anticipated Bensley platform emerges. Interoperability between SATA and SAS makes deploying the ROMB upgrade easier, since the onboard controller will recognize an OS on either type of disk. Switching between SATA and SCSI today doesn't give you such a luxury.

The symbiosis between SATA and SAS has implications way beyond Intel's own motherboard line, though. Resellers now have access to component-level HBAs and RAID controllers that support both interfaces. You can build systems with motherboards featuring board-down controllers. Or tag the right RAID level for your customer, snag an entire platform—backplane and all—and build the perfect storage infrastructure. By drilling into disk controllers, you'll have the know-how to guide such mission-critical purchases.