User`s guide

Chapter 4: SCSI Performance Guidelines 19
chapter 4
SCSI Performance Guidelines
SCSI Performance Guidelines
Pro Tools systems have strict hard drive require-
ments. The recording and playback perfor-
mance of your system depends on several fac-
tors.
Factors affecting system performance:
◆
Hard drive performance. The faster the drive’s
seek time, the better. The data transfer rate re-
quired for 32 track, 24-bit performance (at a
sample rate of 44.1 kHz) is 4.04 MB per second
of sustained throughput. This rate must be re-
flected in the performance of one or more of the
drives and SCSI subsystems in your computer to
achieve this level of performance.
◆
CPU speed. The faster the CPU, the better.
Overall system performance can affect track
count.
◆ Size of your DAE Playback Buffer. See the
Pro Tools System Installation Guide for an expla-
nation of DAE Playback Buffer size and its effect
on system performance.
◆
Edit density (the number of edits per second)
affects the number of different files that a drive
must seek. Sessions with high edit density are
more demanding on hard drives than sessions
with lower edit density. For this reason, drive
performance may depend on the session you are
playing. While there is no specific definition of
high or low edit density, most Pro Tools users
will work with low to moderate edit density ses-
sions. However, extensive use of crossfades, or
certain processing like Beat Detective can create
high levels of edit density in any session.
If you suspect that you are receiving poor drive
performance due to high edit density, use the
Consolidate command for heavily edited tracks.
This will reduce the number of seeks required.
In general, you can obtain the following perfor-
mance goals with the following setups:
To achieve up to 16 simultaneous tracks of 16- or
24-bit audio with heavy edit density, or 32 tracks
with low to moderate edit density, you will need:
◆ One or more Digidesign-approved hard drives
connected to your SCSI adapter card or built-in
SCSI ports. If your sessions have high-density
edits (for example, 3 edits per second across all
tracks, all with crossfades), you will need to dis-
tribute your audio files over more than one hard
drive to allow for increased demand on drive
seek capability.
Make sure to run DigiDrive Tuner to opti-
mize your drive for your Digidesign system.