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Booming SATA Market Looks To Overtake Storage Arena

The high-performance storage interface, which now accounts for a majority of hard drives sold, is opening up new opportunites, as well as challenges.

Eric Hall

January 24, 2007

5 Min Read

And since the speed is just an interface cap, you can also lash multiple independent serial channels together and get very good levels of cumulative throughput by running multiple drives at maximum load. This principle was highlighted in my review of Enhance Technologies' Q14 2.5" drive array, which delivered pretty surprising results when all of the drives in the RAID array were pushing data together. Similarly, a simple RAID array of desktop-class SATA drives can easily stream large data transfers faster than a gigabit Ethernet network can handle. This is one of the reasons why SATA is so popular with the new crop of NAS vendors -- cheap drives are no longer the limiting bandwidth factor.

SATA also provides native support for important features like hot-swapping and command queuing (although they still have to be implemented in the devices, which is not guaranteed with lower-cost units). These features allow the technology to be considered practical for higher-end applications that would otherwise be out of reach for PATA. The thinner and longer SATA cables also allow for better airflow management, which helps to keep today's faster computers running cool.

One benefit that isn't readily apparent, but which has proven to be useful here, is that SATA devices have a common physical connector, which makes resource management somewhat simpler. For example, I can pull a spare from a server array and swap that into a dead desktop system (or vice versa) with no difficulty whatsoever, while the same simply wasn't possible when my desktops were using PATA and my servers were using SCSI. This principle also applies to 2.5" drives (albeit to a lesser extent), in that the common interface means that I don't need special controllers for those drives, so I can do things like clone a laptop drive on my desktop PC with no special hardware or cabling. (There can be some differences in the way that laptop drives handle their LED, but that's a minor penalty.) Along the same lines, SATA also shares a common physical interface with SAS, and SATA drives can (theoretically) be used on SAS controllers. Thus, an easy way to knock $500 off the price of a blade server is to use a SATA laptop drive instead of the more expensive (and perhaps unneeded) SAS drive. The use of a common interface has already simplified some of my recovery operations, and it's already one of my favorite features, even though it isn't one of the common selling points.

Another of SATA's unstated features is the renewed competition that it has spawned over the last few years. SATA is a new technology, so innovators have been presented with a chance to compete on the same footing as older vendors who were established on other architectures, but who do not yet have brand dominance with SATA buyers. Furthermore, the numerous performance and feature benefits that are inherent in SATA's design pretty much apply to everybody, and the only real difference between the players is in their strategy and implementation.

For example, vendors like 3Ware and Areca are pushing SATA performance as far as they can to try and corner the top of the market, while vendors like HighPoint are trying to compete at the low-cost sector with controllers that use device drivers to off-load RAID calculations to the host CPU (thereby eliminating the cost of an onboard dedicated processor). Some vendors, such as Intel, are attacking multiple sectors all at once, with low-end hardware-assist RAID chips, like the ICH7R being sold to motherboard vendors, and feature-rich add-on cards being sold to end users simultaneously. Meanwhile, disk drive vendors like Western Digital are trying to develop the fastest drives possible, while vendors like Seagate are trying to flood the zone with drives for every lifestyle. This rush of innovation and capital investment has resulted in some amazing technology and deals.

On the other hand, the newness of the sector has also resulted in some gaping holes. For example, storage devices other than disk drives have been slow in coming, and can still be hard to find -- there are only a handful of DVD burners that have SATA interfaces, and the number of tape drives with SATA interfaces is also quite limited.

Another problem that has followed from the immaturity in this space is that some implementations are still missing essential functionality that we take for granted elsewhere. For example, the number of controllers with drivers in the Linux kernel can be counted on one hand, and the rest of them either require special builds or do not have workable drivers available at all. For many users, this means that running Linux on a SATA RAID can only be classified as experimental at best.

Just as a simple data point here, the last three server motherboards I've looked at have all included Intel's ICH7R SATA RAID controller on board. Intel provides Windows XP drivers for the controller on its Web site, and it used to provide drivers for Linux 2.4 kernels, but has since made the strategic decision to defer to dmraid for Linux 2.6 kernels. However, dmraid is still only at 1.0 release-candidate status, and currently only supports RAID-0 and RAID-1 on the ICH7R. Due to limitations with the GRUB boot loader, it's not currently possible to actually boot a Linux 2.6 system off an ICH7R RAID controller either. Bottom line: if you've got an ICH7R and you want to run SATA RAID features under Linux, then you'll have to settle for software RAID, or you'll need to start shopping for another controller, because the free one probably isn't going to work. These problems are common with other controllers that don't provide Linux kernel drivers too, and this phenomenon is by no means limited to Intel.

In spite of these difficulties however, it's clear that the performance and features of SATA are plenty good enough for most applications. For these reasons, I've standardized on the technology for all of my systems, and have replaced almost all of my other storage systems within the last year. It's likely that I will acquire a couple of high-end servers that will use SAS, but those will definitely be the exception, if it happens.

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