Hard drives are the centerpieces of your Tapeless Studio. The demands of audio (and video) dictate a fast hard disk with a low seek time. SCSI or EIDE? Or RAID?
You can't very well do disk-based recording without a disk, now can ya? In disk-based, or non-linear, audio recording, we use a computer's hard drive instead of the traditional tape to store audio data. Just as a top-quality analog or digital tape deck is the centerpiece of a traditional studio, the Tapeless Studio must be built around one or more large and fast hard drives. Nowadays, most computers ship with at least a 2 gigabyte Enhanced IDE drive, which is adequate for digital audio. Serious audio and video pros, however, shop carefully for killer drives. Here we'll discuss what to look for in an audio drive, and how to optimize your hard drive for audio recording.
February 25, 1999
The difference between audio (and video) and other types of data is that audio must be recorded and played back in real time. When you record data from a word processor or some such, it doesn't matter how quickly the data gets shuffled around. If your hard drive or some other component is slow, you just have to wait. Audio, however, must be recorded in a a continuous stream. You can't just say to your musicians, "Hey, cats, take five between every verse while the computer finishes writing to disk," now can you? Stereo, 16-bit, 44.1 kHz audio (the CD standard) takes up almost 200k per second, or 10 megs a minute. That means that your data transfer rate, or throughput, must be greater than 200k per second to capture two tracks of audio correctly. Read and write operations must also be uninterrupted. Look for a drive with a high rotation speed and a short average seek time.
As everyone knows, audio files are big, and the better quality, the bigger the file. "16-44" sucks up 10 megs a minute, and a CD's worth of material can be as much as 700 megs. You'll want to allow yourself double that for editing and so forth, and if you plan to use lots o' tracks, you'd better get out your wallet and get 4 gigs or so.
Unlike with analog tape decks, your choice of a hard drive does not affect the sound quality per se. The quality of the sound you get depends mostly on the quality of the original analog signal, and of the analog/digital converters in your sound card or wherever. The speed of your hard drive, however, determines the number of glitch-free tracks of audio that you can play at a time. There's an old saying that a studio sounds only as good as its weakest component. The same is true in the Tapeless Studio. In an analog studio, the issue is noise. In the Tapeless world, the issue is speed. The greater data throughput you achieve, the more tracks you can have, and the less danger of glitches. In most rigs, the hard drive is the constraining factor, or the bottleneck if you prefer. Although it's a bit of an oversimplification, it's safe to say that faster hard drives usually translate into more audio tracks. And, for many of us, the pursuit of more tracks is our life's work.
Back in the old days (a year or two ago), most hard drives made a habit of interrupting the data stream every now and then to perform a thermal calibration (recalibrating the drive to compensate for expansion and contraction due to temperature changes). With other types of data, this was no problem, but it would cause a glitch with audio or video. To avoid the problem, you had to buy a special "A/V" drive (basically a nice fast drive that didn't do the dreaded "t-cal"), although some gadgets like CD-Rs had built-in RAM buffers to get around the problem. Also, the old IDE buss was pretty slow compared to SCSI, so most serious audio dudes used only SCSI hard drives. I haven't heard about the t-cal problem in a long time, and everyone seems to agree that EIDE drives are at least almost as good as SCSI. In fact, audio heads don't talk about drives as much as they used to. The happy fact is that computers and hard drives have gotten so much wickeder and cheaper, that good quality audio with a reasonable number of tracks just isn't much of a problem any more.
But what if I want 16, or maybe even 24, or why not...512 tracks? The table below shows the throughput capabilities of the different busses available. People's claims vary as to how many tracks they can get, but you can probably get 16 or so with a top-end home PC setup. The ultimate in speed is a RAID. A Redundant Aray of Inexpensive Devices couples two (or more) hard drives together, so that you write to both at once. Using disk striping, the data can be sent alternately to one drive and then the other. Since the disk interface (EIDE or SCSI) is faster than the physical drive, you can get much better throughput than with a single drive. This usually requires a separate RAID controller, but I understand that with Windows NT, there is a way to do it all in software, and have also heard of motherboards with built-in RAID.
Maximum system-to-drive transfer speed:
EIDE
16 MB/s
SCSI-2
10 MB/s
UltraSCSI
20 MB/s
UltraSCSI-2
40 MB/s
What are SCSI and IDE, anyway? They are busses. Interfaces that the computer uses to transfer data from one component to another. Most new PCs come with an Enhanced IDE buss for the hard drive(s) and CD-ROM drive. EIDE allows you to plug in up to 4 drives. Whether you have a PC or Mac, you'll need a SCSI adapter card, unless you have one of the new
motherboards with SCSI built in.
SCSI can handle up to 7
daisy-chained devices, including
hard drives, CD recorders, and
removable drives. If you plan to record CDs,
you'll need SCSI, for although there are now a few EIDE CD-Rs, I'd be wary of them.
Okay, so you've bought the fastest, biggest pair of hard drives that you could afford. Now what? There are a few things to think about if you want to optimize your audio setup. First of all, disk compression. Forget about it. Disk compression utilities work by compressing and decompressing your data on the fly as you read and write. That won't hack with audio, because the utility won't be able to compress and decompress fast enough to achieve the necessary throughput. You'll get erratic performance at best. If you must, you can partition your hard drive and compress the part with the programs on it, reserving an uncompressed partition for audio.
If you can, use a separate disk for your audio. Swap files, program files and other stuff can interfere with your throughput when they are on the same drive that you're writing audio to. Also, it's recommended to defragment your audio files regularly, so it's handy to have it on a separate drive. If you don't have two disk drives, you can partition your drive to create two virtual drives.
Now, every computer nerd knows that data on a hard disk must be backed up periodically to some physical medium, and your precious audio tracks are no exception. Naturally you want to cover your bum in case of a hard disk crash. Also, because audio files are so large, when you get done with a project, you will want to purge it from your hard drive to make room for the next one. But in case you want to return to that project in the future, you need to make a permanent backup. What if you are recording audio CDs? If you want to go back and make changes later, you could just capture the data from the audio CD, and go from there, but beware! Capturing audio CDs is a dodgy business, and the error correction is not as robust as when you save a computer wave file. To be on the safe side, I always make a CD-ROM of all my wave files, once I get them finished.
Using your CD recorder for backup is a way to kill two birds with one stone, but there are other options. DAT tape may be used to back up computer data, either with a SCSI computer DAT drive or a regular audio DAT recorder. Removable disks are also very handy. For a while, floptical, Bernouilli, and a few others were battling it out, but these days Iomega's Zip (100 meg) and Jaz (1 gig) drives are all the rage. If you want to back up as you go, the non-rewritable CD-R format will get expensive (and wasteful). Removable disks can be recorded and erased as you wish, making them perfect for periodic backups and moving data between different studios. The beauty of an external Zip or Jaz is that the drives themselves are small and handy. If you need to take a file to a friend's house, just take the whole drive, and it doesn't matter whether they have one or not. The Iomega drives come in either serial-port or SCSI versions. I find the SCSI external Zip most convenient, because it allows me to exchange files with Mac shops if I need to (Macs all have SCSI).
So, what's the ultimate? Well, a pair of 2-gig EIDE or SCSI drives will stand you in good stead. A man also needs a CD recorder, and a removable. For the future? UltraSCSI RAID running under Windows NT, a rewritable DVD, and a partridge in a pear tree! Happy 2000!
