R AID: Redundant Array of Independent Disks. RAID is the technology that allows computer users to use multiple hard drives as one large and/or fast drive. The main two versions allow for speed (called striping), or for redundancy (called mirroring). A quick Google search offers this fairly accurate and concise explanation from Infortrend, a RAID vendor:
Data Striping: Data is split across multiple drives in a RAID array to form a single logical storage unit. Each driveis storage space is partitioned into stripes, ranging in size from one sector (512 bytes) to multiple megabytes. The stripes then are interleaved so that the logical storage unit is made up of alternating stripes from each drive.
Mirroring: Used in RAID levels 1 and 1+0 for data redundancy. Data is duplicated through mirroring across two [or more] disks. If one drive fails, the data remains available on the other disk. Itis sort of like low-end clustering.
Parity: Information used in RAID levels 3, 4 and 5 for data recovery. In the event of a drive failure, parity information can be combined with the other remaining data to regenerate the missing information.
Each of these types of RAID has its advantages and weaknesses, but thatis a topic for another discussion. Today, we are looking at a hardware RAID solution called the Vanguard II Series from FirewireDirect, which offers both striping and mirroring.
What is a hardware RAID?
RAID systems used to be expensive, but FireWire began to change that shortly after Apple introduced it in 1998. FireWire RAID systems today can be had for as little as a few hundred dollars for a JBOD setup (Just a Bunch Of Drives), scaling upwards to more than US$10,000 for as much as 2.52 terabytes. Thatis more than 2,500 GB for those keeping score at home. With many of those systems, itis as easy as plugging the drive in, and saving data as either RAID 1 or RAID 0 drive, and using it like any external storage device.
Consumer pricing on FireWire RAID products has reached new lows, and places the power of RAID into the price-range of more people. This is in part because todayis Macs and PCs are powerful enough to make software-driven RAID usable. The inexpensive RAID solutions are almost always software-driven, and that works quite well for many applications. Hardware RAID, on the other hand, is a bit pricier, but can offer more flexibility, and greater reliability.
Hardware RAID systems differ significantly from software RAID systems specifically because the RAID functions themselves are controlled by on board hardware (hence the designation "Hardware RAID"). In other words, the drive itself is smart, and handles many of the tasks that would otherwise be handled by your computer. Software RAID, as the name implies, is controlled by software on your Mac or PC, and uses the processing power of your computer for those same tasks.
The benefit that hardware RAID can offer is two-fold: With hardware RAID systems, your Mac is dumping the data off to the RAID system itself without having to mess with actually writing it to the platters. This can make a noticeable difference when doing CPU and I/O intensive chores like DV editing, working with large publishing files, or graphic design work using really large files.
The other benefit that comes with using a hardware RAID solution is with RAID 1. RAID 1, or mirroring, means that if you have two (or more) drives in a RAID, they will each mirror the data. That means that if one drive fails, the other drive (in the case of a dual-drive system) will still have all your data. Perhaps more importantly, such units can do so without using your Macis processing power if they are in use. It can also back itself up while simultaneously functioning as your drive, if you are in a situation where you are willing to take the risk that the second drive will not also fail.
Vanguard Series II
Such is the case with FirewireDirectis Vanguard Series II, which we tested for this review.
The Vanguard Series II FireWire RAID solution is a dual-drive hardware RAID. The unit features a lockable glass door, metal casing, and an LCD readout that tells you what the drive is doing. The company sells the drive in five configurations: 80/160GB, 240/120GB, 400/200GB, 500/250GB, and as enclosure kit.
In our testing, we used the drive as a file server, as a back up solution, and simply hammered on the drive with repeated file transfers. In addition, we took the drives out of the unit to test the its ability to rebuild itself in RAID 1 mode. Throughout our extensive testing period, the drive performed well, if noisily, and the functional design of the system made it easy to swap out drives.
The Vanguard Series II has a loud fan, making it impractical for desktop use, unless you are also working with a loud computer, or donit mind noise. The noise output of the unit makes it better suited for use under a desk, in a server room, or some other place away from your work space.
Because it is a hardware RAID, changing the unit from RAID 0 to RAID 1 is handled with a simple switch on the back. There is also a power switch on the back, and the drive uses a standard three-pronged plug, and comes with a power cord. There is no software needed to run the drive on your Mac; its hardware RAID nature means that your Mac sees it as a single drive, and thatis that.
Hot Swappable
The drives are mounted on rails that slide out with a simple lever. Each drive is mounted with standard hard drive mounting screws on the rail, and were able to change them out in a couple of minutes. Take the drive out by sliding it out of the case, replace the drive, and slide it back in. The drive will plug itself in to both power and a data connector when it is pushed in all the way.
If you are mirroring (RAID 1), the system will detect the new drive and commence backing itself up. This process takes several hours, depending on how much data you have, as the drive copies itself over sector by sector. While time consuming, that offers a much more reliable back up. You can interrupt the process, even powering down if necessary, and when you power the drive back up, the rebuilding will commence from where it left off. In testing, the unit performed this task perfectly.
Performance
RAID systems were originally proposed to make larger (and faster) storage volumes available in era where desktop PCs came with drives measured in the 10s of MB. With FireWire, the limitations of the FireWire bus itself offer a much lower ceiling on performance than does the RAID controller (software or hardware), or the physical hard drives. That means
| Speedtoolsis QuickBench 2.0 results. (Click each image for a larger view) |
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|---|---|
 Bar graph results (longer bars are better) |
 Text results (larger transfer rates are better) |
 Extended Tests, Small Files (higher performance figures are better) |
 Extended Tests, Large(r) Files (higher performance figures are better) |
These results show that in most tests, the Vanguard unit hits the 30 MBps level, which is basically the limit with current FireWire bridge technology. Our real-world time tests showed slower results that were in the 16.3 MBps range. This is consistent with other real world testing we have done with other FireWire drives, but again, the strength of hardware RAID is that it requires far less system resources from your Mac to do its job.
Conclusion
FirewireDirectis Vanguard Series II is a drive aimed at people who need a very reliable back up solution, and people who need to squeeze every single ounce of power out of their Macs. We found it to work very well for these types of tasks. The unit is easy to work with, solid, and performed reliably for the many weeks of testing we put the unit through. The biggest drawback we found was the high level of noise that comes from the fan, which could be an issue for some users.
Because it is a hardware RAID, you have to pay for all those qualities, but to those who need them, the expense will be worth it. What the drive is not designed for is people who need an inexpensive way to get a really large volume. For those solutions, software RAID is the way to go.