RAID 1+0

The best of both worlds, the RAID 1+0 combination approach yields great results! Right?

The mix-and-match of RAID setups, RAID 1+0 offers a unique combination of RAID 0 performance with RAID 1 data protection. It’s one of the proud members of the “nested” category of RAID configurations. Like peanut butter on bread, a nested RAID uses one RAID configuration as the base for a second RAID. This hybridization gives you a chance to reap the benefits of both setups, although you’ll never achieve the ultimate benefits of either.

Each RAID controller will handle the setup of the RAID 1+0 config differently, and some won’t even support such fancy storage dreams. Whether the controller defaults to RAID 1+0 or forces you to create an array on top of an array, the basic premise is still the same.

You’ll need at least four hard drives to create a RAID 1+0 setup. Logistically, the drives are split into two pairs. Each pair operates as a mirrored array, or RAID 1. The two pairs are then chained together in a RAID 0 configuration. This gives you data redundancy on the micro level, while still giving you speed and storage benefits on the macro level. You’re safe from data loss as long as you lose only one drive per mirrored pair. You’ll face the same data loss problem that plagues individual RAID 0 arrays if both drives in either of the mirrored pairs suffer an untimely demise.

Hands On

RAID 1+0 performance is far superior to that of a single Raptor drive. But that’s like saying ice cream is tastier than cat food. Two Raptors in a RAID 0 configuration still dominated in the average write portion of our HD Tach benchmarks. And that makes complete sense, as the mirroring portion of the RAID 1+0 array reduces its performance.

RAID 1+0’s average read speeds, on the other hand, are higher than those of two Raptors in RAID 0, but that’s not so much an issue of technology as it is one of scalability. Just for giggles, we fired up four Raptor drives in a striped RAID to get a true, four-drive showdown. The four-drive RAID 0 mercilessly decimated the benchmarks of our RAID 1+0 setup. Average read speeds were 38MB/s faster and average write speeds were 43MB/s faster. If you’re willing to risk catastrophic data loss, RAID 0 is still a speed demon’s friend. But you certainly won’t suffer, speedwise, with a RAID 1+0 array.

Make a RAID with Windows

If you want the size benefits of a striped array but don’t feel like setting one up using your motherboard’s controller—or if your motherboard doesn’t include a RAID controller—you can actually create a large, striped drive in Windows itself. Just head over to your computer management screen (you get to it by right-clicking Computer in the Start Menu and selecting Manage). Convert the drives you want to stripe to dynamic disks, then create a new volume and select “striped” for the configuration. Voila! The speeds of the array won’t be nearly as fast as those of a controller-based striped array, but they’re still noticeably faster than a single Raptor’s, with the added benefit that your data isn’t tied to a controller that’s soldered onto your motherboard.

Best scores are bolded. HD Tach measures hardware-based volumes and cannot run benchmarks on software-based RAID solutions.

RAID 5

Parity makes a world of difference and barely hurts speeds.

Like RAID 1+0, a RAID 5 configuration is a hybrid combination of data safekeeping and speed. But unlike the former, RAID 5 doesn’t rely on mirroring to preserve your information. It instead uses an alternative method of data redundancy found in RAID setups—parity.

To get into the fine nuances of how parity works would require Excel charts, lots of binary code, and acronyms—lots of acronyms. So we’ll generalize. The mathematics of parity dictates that if you have four drives in an array, the RAID will split each piece of data into three stripes. Each stripe will go to a single hard drive, as it would in a RAID 0 configuration.
The controller then creates a parity stripe based on the three stripes of data. A parity stripe is a logical calculation that allows the controller to re-create any individual stripe that becomes corrupt (or in the case of a drive failure, nonexistent). Similar to mirroring, the lost data is made available to the host machine instantaneously. But the loss of a single drive puts the entire array at risk. Should an additional drive fail—making that two of the four drives dead—all the data on the array is lost. A parity stripe works wonders, just not miracles.

Hands On

RAID 5 gives you the best combination of speed, size, and data savings. Our RAID 5 and RAID 1+0 arrays scored similar speeds, with the RAID 5 squeezing 15 additional MB/s in our HD Tach average read test.

The bonus comes in the fact that our RAID 5 array gave us an additional drive’s worth of space to play around with—450 total gigabytes as opposed to the RAID 1+0’s 300GB of total capacity.

Admittedly, a RAID 1+0 array gives you better data redundancy on paper, but the additional mirroring seems like overkill. In essence, you’d be performing the same maintenance tasks you’d be performing in a RAID 5 array. If a drive goes out in a RAID 1+0, it would be in your best interest to stop what you’re doing and immediately replace the dead drive; the same goes for RAID 5. While the next drive that goes out in your RAID 1+0 array might not be the one to destroy a mirrored pair and consequently your data, do you really want to roll the dice? We wouldn’t, and we’d much rather have the performance and size benefits a RAID 5 array brings.

Why Use a Controller?

All of the benchmarks in this feature were completed using Adaptec’s RAID 31605 controller ($1,000, adaptec.com). In our initial tests, we found that our EVGA 608i chipset-based RAID speeds simply paled in comparison. Thanks to an onboard 800MHz processor and 256MB of DDR2 cache memory, the controller was able to output an average read speed of 211.7MB/s in a simple HD Tach benchmark of a four-drive, striped array. The motherboard-based RAID topped out at 118.9MB/s.

RAID controllers also offer more options and safety features than a motherboard-based chipset, and the motherboard RAID itself is limited to the number of free SATA ports you have. In contrast, our controller supports up to 16 SATA drives.

Best scores are bolded. Arrays were tested using a four-drive RAID 0 configuration.