Experience local shipping options and optimized product inventory for your region.
RAID Options for the G4
by Steve Manke A Redundant Array of Inexpensive Drives, or RAID as it is often called, has been a great way to get exceptional performance out of an every day computer. Until recently, RAID configurations where reserved almost exclusively on high-end servers or places where vast amounts of data needed to be accessed quickly. In any RAID configuration, the RAID controller card is what determines how data is written across each of the array's drives. A Level 0 RAID consists of at least two drives connected to a controller card. For the purpose of this review, I have focused on a Striped Level 0 RAID configuration consisting of 2 45GB 7200 RPM Maxtor drives. In a Striped Level 0 configuration, the controller card formats the drives in a tandem configuration. In the eyes of your Macintosh (or, sadly, your PC), the two drives become one. In my case, the two 45GB drives become a single 90GB drive. In a normal configuration, your Mac writes data to the drive one chunk at a time in a sequential order. One chunk resides right next to the other, filling sector after sector of your hard drive (see figure A-1 below). In Level 0 RAID, the computer sends the data to the controller card where the card directs block one to the first drive, block two to the second drive, block three to the first drive, block four to the second drive and so on (see figure A-2 below). This is known as Striping.
With the RAID controller card installed, your computer writes data to the drive bus as if nothing unusual were going on. It is the RAID card that directs the information in a more efficient manner. The way the RAID directs the information equates to an increase in disk performance for the computer. A Level 0 RAID provides much more efficient disk performance in that the second chunk of information can be written to the second drive even before the first drive has finished writing the first chunk. Data flows more quickly because it is being dumped on to the disk drive more efficiently. For this reason, this RAID configuration is considered optimum for video editing systems or high-speed file servers. Since RAID cards are not priced with the home user in mind, a niche was opened in the software market. SoftRAID LLC then released SoftRAID. As the name suggests, this product did the same thing as the hardware RAID's controller card but it did it in the computer's software. Just chain the SCSI drives together using your SCSI ribbon and use SoftRAID to configure them as a RAID in a simple graphical interface. The standard rules of a RAID configuration allow only the use of SCSI drives. But when ATA expansion cards hit the market, they shook things up a little bit. Some of the ATA cards actually assigned the IDE drives SCSI addresses. So, similar to the way that the RAID card made the computer think there was only one hard drive attached to it when in fact there where two drives working as one, these ATA cards made the computer think that it was using SCSI hard drives when in fact the attached drives where IDE. With that, suddenly SoftRAID could be used on any Mac with an IDE bus. And just as SoftRAID LLC saw the opportunity to fill a niche in the market, Sonnet saw the same niche and was the first to fill it with a hardware solution. Having offered ATA cards to Mac owners as a means of adding additional ATA buses to their machines, and given the fact that those cards where masking IDE drives with SCSI addresses, Sonnet introduced the Tempo RAID 66 IDE card. This ATA card does on a hardware chip what SoftRAID did in the computers RAM. With all of this information in mind and all of the options now available, I wanted to compare them in a real world test. I used 2 45GB 7200rpm Maxtor drives for this test since they are in their own right very fast drives. And since I was testing them in a G4 Sawtooth 350MHz, I included some benchmarks with the stock Quantum 10GB 5400rpm drive that shipped with the system. For the purpose of comparison, I did a series of bench tests to get the most of the drive comparisons. I used MacBench 5.0 as a means of comparing the RAID performance in a time tested environment. I also tested the drive configurations using Atto's Disk Benchmarking software. This was useful for determining both the peak and sustained read/write time of the drives. Going a step further, I used the Finder and a stopwatch to get the most 'real world' comparison of how quickly I could duplicate a single 500MB file on each of the configurations. And since my goal was to compare software and hardware RAID's to each other as well as to my default G4's system drive, I also did a benchmark using one of the 45GB Maxtor's in a non-RAID configuration. The benchmarks are as follows: MacBench Results*: * In order to use MacBench, the computer must be booted from the drive that the test is to be conducted on. Since the version of SoftRAID that I used did not allow the RAID volume to be bootable, I was unable to compare it in this portion of the test. Note that in the benchmark titled 'Disk Test,' the hardware RAID showed little improvement over the drives normal performance. But in the bench titled 'Publishing Disk,' the RAID's performance shifted to have a clear advantage. In a desktop publishing environment there are a wide variety of tasks that access the computer's hard drive, this test is much more disk intensive. Situations occur where there are both brief hits on the drive as well as prolonged accesses in which the software might use the drive as virtual memory. Read & Write Performance: Note how the Hardware RAID maintains an unprecedented consistency between both the sustained and peak scores in both the read and write tests. In writes, the SoftRAID out performs the base 45GB drive by nearly 2MB per second, but in sustained reading, the drives score actually under performs the base drive. Real World 500MB File Duplication: This test does the best job of showing what is truly gained from each of these options. The most cost-effective way to increase the G4 350's performance is to simply replace the stock drive. Looking further, you see that the SoftRAID solution shows only a slightly better score than the base 45GB drive. And the hardware RAID clearly takes better advantage of the drive hardware by offloading the controller's function to the onboard chip. In the end, if cost were the primary consideration, I would simply add a new hard drive to the computer. IDE drives have become more popular with the average user than SCSI for good reason- the drives themselves have become faster and less expensive. If you are interested in the best possible disk performance, as I am, I think the Hardware RAID card speaks for itself. Its scores show consistently better marks across the board. Even through $200 is quite a bit of cash for a PCI card, it's still much more cost effective than a SCSI RAID controller card, and the drives are vastly more affordable. In my case, I like to play with digital video; I put my money on the Sonnet card and have been very happy with the Maxtor 45GB drives. If data integrity is of paramount importance, don't overlook the SoftRAID solution. While it did not fare as well as the Sonnet card in a Level 0 RAID, the same software package can be used to configure the same two drives into a Mirrored Level 1 RAID. In such a scenario, data is simply mirrored from one drive to the next in real time. Should either drive fail, your data will still remain intact on the other drive. In many ways the Level 1 RAID is the best possible backup solution for important data. If you are planning on adding a SoftRAID to your system and you already have an internal IDE bus, you will still need to add some sort of aftermarket ATA adapter. The Mac's onboard controller does not mask IDE drives with SCSI addresses and therefore is not capable of being configured as a SoftRAID. Sonnet offers a non-RAID Tempo ATA PCI card for about $99. VST also offers an ATA card that comes bundled with SoftRAID for $89.95. One of the other nice features of the Sonnet Tempo RAID is that it can be configured to do either a Level 0 Striped or a Level 1 Mirrored RAID with just the flip of one switch on the card. The card is also capable of driving a total of 4 drives in either configuration. One card will allow you to add up to two logical volumes to your G3 or G4 in either a Level 0 or Level 1 configuration. Sonnet tech support also noted one other interesting fact about the Tempo RAID- the product documentation specifically lists the cards as working in only G3 or G4 computers. While the card can add the same capability to older computers such as the Power Mac 9500, the card does not offer any performance gains. All tests where conducted with the following system configuration:
|