The Big the Fast and the SCSI - SCSI versus IDE versus SATA

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SCSI vs. IDE
So what are the basic differences between SCSI and IDE devices' IDE has been the standard interface for hard drives on the PC for many years and now on many Macs. It's a two-channel standard that supports up to four devices, two per channel. Over the years hard drive makers and motherboard suppliers have improved the IDE standard. Today's IDE drives referred to as enhanced IDE or EIDE drives are often called Ultra ATA or Ultra DMA drives. The latest versions of IDE drives include smarter and faster cache memory for buffering data to and from the drive. And today's motherboards can move data around a lot faster with less attention from the microprocessor. Different hard drive makers use various combinations of acronyms and numbers to describe essentially the same technology. The 33, 66, or 100 that follow the ATA and DMA in the specification refers to the burst transfer rate. The higher the number the better. And as the burst transfer rate has increased over the years so has the sustainable transfer rate. This is the amount of data that can continuously flow from the drive to your system. An example of a high performance 7200RPM hard drive is the 75GXP from IBM. This ATA 100 compliant drive delivers 45GB of storage (about 86 hours of two track 44kHz-16bit audio), 8.5ms access time, 2MB data buffer, and a sustained transfer rate of 37MB/sec. Best of all you can pick this drive up for under $300. A system properly matched with this drive(s) would offer excellent performance for any digital audio workstation (DAW). The 75GXP is a good drive to use as a benchmark against other Ultra66/100 you may be considering for an IDE based system.

SCSI systems are generally considered to be faster and more robust than IDE systems. In the past IDE systems were usually significantly slower than SCSI systems. However, today the speed of Ultra DMA 66/100 drives combined with faster processors and controller cards offer performance on par with SCSI systems for less money. However, high performance SCSI systems such as Ultra160 SCSI are more appropriate where high bandwidth and multiple drives are required. High-end audio and video editing systems typically use some flavor of SCSI. Unlike IDE devices that share a channel and have to wait for each other to use the channel, SCSI devices can operate simultaneously on their own bus. These devices can read and write data simultaneously. Once again depending on your applications using SCSI can pay dividends in saved time. But you will pay for the performance. For example, the Quantum Atlas 10K Ultra160 drive in a 9.1GB capacity with 5ms access time and 26MB/sec sustained throughput sells for almost $400. You get 35Gigs less storage and pay a $100 more compared to our IBM drive above. Is this performance premium worth it' Quite honestly for most folks probably not. But I've never had anyone complain to me about their files opening to fast or their video projects not taking long enough to render.

Speed Kills
But there is a downside to having the fastest drive on the planet. In general, higher RPM drives require more power, are noisier, and will suffer more "wear and tear" on the drive components. This higher stress on all moving drive components can decrease mean time between failure (MTBF) ratings. The good news is suppliers are working to optimize performance while decreasing noise and improving drive reliability. So stay paranoid. It doesn't matter if your drives are new or old. Sooner or later they will fail. So backup...backup'backup. There, I've said it.

Single vs. Multiple Drive systems
One way to improve your system performance is to keep your operating system and programs loaded on one disk and your data loaded on another. This is a simple two-drive setup. All that is required is popping open the computer case and adding a second drive. For even better performance you may want to consider setting up multiple hard drives with a RAID controller. Short for Redundant Array of Independent Disks, RAID systems can be used in a variety of ways. The most common use in Audio Video editing applications is a high performance RAID configuration referred to as Level O. This RAID level uses data stripping that spreads out blocks of each file across multiple disks. Even just two hard disks in a disk array can offer a dramatic performance increase. The Promise FastTrack-100 Ultra100 IDE-RAID controller is an excellent choice for IDE drives and the MegaRAID Express 200 from AMI is an excellent choice for Ultra160 SCSI systems.

I recently put together a 1GHz Athlon system with 383MB memory and two Quantum Atlas 10K drives in the above mentioned Level O disk array. And I'll tell you when I'm mastering in T-racks or playing with the mix in Cool Edit or Vegas the speed difference is worth it to me. However, this system is noisy as heck and I'm not always taking full advantage of the speed. In fact, I often use my quieter IDE based, no disk array, K6-3 system for multitrack recording because I'm one of the suckers doing all my work in a 10x10 room. Not to mention during the summer months the last thing I want is a space heater in the room. Which brings us to our next point of consideration.

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