Installation guide

TDM Installation Guide 6
SCSI Cables
Use shorter SCSI cables to improve reliability.
Table 1 provides guidelines for maximum cable
lengths according to SCSI type.
Disk Space for Audio Tracks
Audio tracks recorded at 24-bit resolution at a
CD-fidelity sampling rate of 44.1 kHz require
about 7.5 MB of hard drive space per minute.
The same tracks recorded at 16-bit resolution re-
quire about 5 MB per minute. Stereo tracks will
require about twice as much hard drive space.
Using these guidelines:
• 64 mono tracks of 24-bit audio takes up about
480 MB of hard drive space per minute.
• 64 mono tracks of 16-bit audio takes up about
320 MB of hard drive space per minute.
• 32 mono tracks of 24-bit audio takes up about
240 MB of hard drive space per minute.
• 32 mono tracks of 16-bit audio takes up about
160 MB per minute.
A 9-gigabyte drive holds:
• 18 minutes of 64 tracks, 24-bit audio
• 28 minutes of 64 tracks, 16-bit audio
• 37 minutes of 32 tracks, 24-bit audio
• 56 minutes of 32 tracks, 16-bit audio
Distribute Audio Across Multiple Drives
For best recording and playback performance,
don’t record and play back all audio files in a
session from the same drive. Instead, use
Pro Tools disk allocation features to distribute
audio files between multiple SCSI drives. See the
Pro Tools Reference Guide for details.
Separate Video and Audio Files
If you are working with imported movies, movie
files must reside on a different SCSI bus than au-
dio files. If audio files reside on disks connected
to a SCSI HBA card, video data should reside on
drives connected to a different SCSI bus.
Dual-Channel SCSI HBA Cards
If you use a dual-channel SCSI HBA card, equally
allocate audio files to drives connected to each
of the two busses on the card for optimal perfor-
mance.
Table 1: Maximum cable length and number of drives
supported according to SCSI type
SCSI type and
transfer rate
maximum
cable length
maximum #
of drives
Fast SCSI
10 MB/sec
3 meters 8
Wide SCSI
20 MB/sec
3 meters 16
Ultra SCSI
20 MB/sec
(8-bit narrow)
3 meters 5
Ultra SCSI
40 MB/sec
(16-bit wide)
3 meters 5
Ultra SCSI
20 MB/sec
(8-bit narrow)
1.5 meters 6–8
Ultra SCSI
40 MB/sec
(16-bit wide)
1.5 meters 6–8
Ultra2 SCSI
Low Voltage Dif-
ferential (LVD)
80 MB/sec
12 meters 16
TDM_Install.book Page 6 Saturday, January 13, 2001 9:35 PM