by D. Glen Cardenas and Jose M. Catena Cont. from Page 8; Back to TOC |
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When it comes to picking a drive for a DAW, you have a bit of a job ahead of you. We looked at the two contending formats in the last sections, but that's just an overview. What about the specifications? What do you need to know about a drive's performance in order to make an intelligent choice regardless of which format you're interested in? As it turns out, the specifications of both the drives and the controllers can lead you quite clearly to the best choice so long as you don't loose track of what you're after. You want a disk for streaming media and you're not attempting to set up a server, so many of the drive specs and controller advantages don't apply and others will count more heavily. On the other hand, you're not just going to be typing email or surfing the net on this system either, so not "just any old drive" will do. To an extent, the drive format you have already committed to will be a big factor. If you don't want to support a large number of drives and CD devices, IDE will look like the best path to follow and SCSI will be much less appealing. If you already have SCSI, then the choice is clear. If you are building from scratch, you should at this point have a good idea what CPU you would like to run, how much RAM you will need, what you feel is right as far as video, sound, and perhaps LAN cards go, and if you want an internal modem. Your choice of mother boards and disk system are now at issue. Should you spring for SCSI and should you get a mother board with built-in SCSI support? Is IDE the best way to go? Does it really matter? We can't answer these questions for you, but we can give you better tools for reaching that decision yourself with less dependence on the common DAW disk superstitions, misconceptions and other people's unfounded prejudice. Just for the record, no amount of care in picking a drive will offer you advantage if you don't do a few simple optimizing steps on your own. For one thing, defragment your data partitions often. Keeping large file access sequential will allow your drive's performance qualities to shine. Also, store your data in the front tracks of the drive (first partition) or as close to the front as you can. As the track numbers get higher and the tracks get closer to the spindle, the "zoned formatting" of your drive will result in fewer sectors per track as you move toward the spindle. The more data you can pull from a single track, the faster the throughput. The outer tracks with the higher sector count will hold more data, thus offering up to 60% faster read/write throughput compared to the inner tracks. For another thing, if you are using FAT32 partitions for your system, consider reformatting the data partition as a FAT 16 drive. This will limit you to a 2.1 gig partition, but the larger cluster size is an advantage in streaming media throughput. The system must stop reading data to reference the FAT table less often if the cluster size is large. Yes, the same can be done with FAT 32, but the partition must be above 32 gig for those advantages to start appearing in a FAT 32 partition. We discussed how to force your FAT 32 operating system to generate a FAT 16 partition in part 1, "A Question of Drives". Naturally, if you're running Windows NT or Windows 2000, you can use the NTFS formatting system, but FAT 16 may be faster even under NT. That said, let's look at the guts of a hard drive. Media Access Speed This section will not be much of a comparison between IDE and SCSI in that both types of drive are, from a "between the shells" point of view, the same. They have a sealed case with one or more platters of magnetically coated media, a small synchronous motor designed to rotate the platters at a precise speed, and an actuator with one or more arms attached, each with a read/write head at the tip. The platters hold the data in the form of concentric tracks, each split like a pie into many sectors. Each sector will hold 512 bytes of user data as well as error correction information and other alignment information. The actuator is designed like a speaker voice coil, extending or retracting along its throw path depending on the strength of an electrical signal in the coil which will force it very precisely to any location. The arms attached to the actuator are thereby positioned to various places above the spinning platters where the heads can pick up or lay down streams of magnetic information. The heads float on a cushion of air at a distance of about 10 microns above the platter surface. The platter's rotation produce that cushion of air. In contrast, a particle of smoke is about 100 microns in size, or 10 times the head gap. For this reason, these drives are manufactured in very closely controlled "clean room" conditions, are sealed at the factory against any interaction with the outside environment and sold with the expressed condition that the user never, for any reason, open the drive casing. The drive also has a circuit board to control the mechanism and coordinate the transfer of data to and from the platters in a specific format. Aside from the data and power connectors, that's about the whole story. It stands to reason, therefore, that the physical properties of these moving parts hold the key to a drive's access speed and data throughput. In reality, this is more the case than is commonly believed, and for that matter, commonly disclosed by the drive manufacturers. So many drives are advertised with little more than their data storage capacity and interface burst transfer speed. Neither of these factors relates directly to a drive's usability as a DAW storage system. To get the real story, you must dig into the drive specifications, usually available only on the maker's web site and even then only after linking past several pages of ad hype and chest pounding. The drive actually performs two distinct operations in order to read or write data, those being head positioning and data transfer. Let's start with head positioning. To perform this act, the drive must:
All of this positioning
and the buffering of the data to be written or that is finally read must
be controlled by the drive electronics. Although the electronics is quite
fast by all accounts, there is still a certain amount of overhead associated
with this activity. It is referred to as... you guessed it, Controller
Overhead. Sometimes this spec will be listed for the drive and is usually
the same over a given product line or at least a given model range. It
is expressed in milliseconds (thousands of a second), or "mSec". Go to Page 10 (Part 4); Back to TOC |
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