This article discusses what kind of hard drives are appropriate for video capture and playback using Final Cut Pro, as well as discussing specific incompatibilities between certain hard drive system and hardware combinations.

Digital Video can take up an enormous amount of storage space. While the internal drive that comes with your computer is acceptable for DV capture; fragmentation issues, limited drive space, and high data rate M-JPEG capture may prompt you to seek additional storage space. When capturing or outputting video, it is essential to use storage devices with high enough performance. Whether you are editing material imported from DV, or M-JPEG clips captured using a Targa or Igniter card, it is important that your hard drive meet the bandwidth requirements necessary to avoid dropping frames. Dropped frames can affect sync and also prevent seamless playback (see article 58640: " Dropped Frames and Loss of Audio Sync ").

When comparing different kinds of storage, the three factors that users must consider are sustained transfer speed, seek time, and spindle speed.

Sustained transfer speed is a measurement of how much data can be written to a drive in a given period of time (megabytes per second). When using capture cards utilizing M-JPEG compression (for example, the Targa or Igniter cards) the higher the sustained transfer speed of a hard drive, the higher the quality of video that can be written to it. (For imported DV material, this is not as much of a concern as DV has a fixed data rate that does not vary.)

The second factor, seek time, is a measurement of how quickly data stored on the drive can be accessed (measured in milliseconds). Low seek times are important to Final Cut Pro, as an edited sequence of movie clips causes the drive to spend a lot of time searching the drive looking for the next movie clip to play.

The performance of individual drives will also vary according to their design and spindle speed. Higher spindle speeds help increase a drive's sustained transfer rate (typical multimedia drives run at 7200rpm), but also cause the drive to heat up the faster they run, so ventilation is an important consideration when installing such drives either internally or in external enclosures.

There are currently four categories of storage devices available to consumers. Each of these catagories has advantages and disadvantages depending on what kind of video you may find yourself working with. These catagories are:

Removable Storage

This first catagory, which includes recordable CD-ROM, Iomega Jaz or Iomega Zip drives (and excludes removable SCSI drives) can be disqualified out of hand for video capture. While these devices are often used for project backup or to transport broadcast quality Quicktime clips from one editing suite to another, none of these devices provide the data throughout necessary for real-time, broadcast quality video capture or playback.

Firewire drives

These drives are not currently recommended for video capture or playback with Final Cut Pro. We are in the process of testing various FireWire drives as they come out. These drives are suitable for the backup and transport of broadcast quality Quicktime clips from one editing suite to another, and due to their ability to be hot-swapped, are particularly valuable for this task.

Ultra ATA or EIDE drives

These drives, while not as high performance as LVD SCSI drives (described below), have found use amongst many editors using DV equipment. Imported DV material has a fixed data rate of approximately 3.5mb/sec, and high performance Ultra DMA EIDE/ATA-33 or -66 drives are generally capable of importing and outputting these streams. Beware that the sustained transfer speed of the drive you consider is 8MB/sec or above, that it's at least a 5400rpm drive (see spindle speed below), and that the average seek time is below 9ms if you plan on using these drives. Also, these drives can only be installed internally.

Power Macintosh G3 (Blue and White) users will need to obtain a third party accelerated ATA interface in order to install additional EIDE/ATA drives, as the built-in ATA interface is taken up with the internal hard drive and the CD-Rom. (Certain platinum G3 systems may already have unused ATA ports available.) Such an interface will occupy one PCI slot and may support up to four additional internal drives (installing more than two drives may require a special third party bracket). Power Mac G4 users have a built-in ATA-66 interface socket available for use with one additional drive. (Early 350mhz Power Mac G4 models may lack this and require a 3rd party accelerated ATA card.)

SCSI drives

SCSI drives are currently the highest performing drives available. SCSI (Small Computer Systems Interface) has been implemented in a number of different ways over the years, with each successive type of SCSI achieving higher and higher performance. The current standard of SCSI for video capture and playback is Ultra2 LVD (Low Voltage Differential) SCSI . Ultra2 SCSI drives alone have high enough performance to capture and output M-JPEG video at high data rates.

A G3 or G4 Macintosh will require an Ultra2 SCSI interface in order to use these drives if one is not preinstalled (this card will occupy one PCI slot). Both Atto and Adaptec make Ultra2 SCSI cards that will work with Final Cut Pro. SCSI drives may be installed either internally or externally, although for superior cooling and mobility, many users prefer external cases. The Ultra2 SCSI interface card will allow the connection of up to 14 SCSI drives, although typical users will usually have no more than four. Drives are connected in a daisychain fashion, with each drive connecting to the one before it, and the last one being terminated.

When connecting multiple drives, high quality, shielded cables must be used to prevent data errors. Preferably these cables should be as short as possible (3 feet each or less), as excessive cable length can also cause difficulties.

Figure 1 Daisychaining Ultra2 SCSI drives together using DB-50 SCSI cables

There are many kinds of SCSI drives that are slower than Ultra2, and while devices such as scanners and removable storage can also be connected to the same interface, to achieve the desired level of performance only Ultra2 SCSI drives should be connected to your Ultra2 interface. Otherwise the entire SCSI chain will run at the speed of the slowest connected device, impeding performance and causing dropped frames on capture or playback.

While Ultra2 SCSI has a maximum transfer speed of 40mb/sec, the actual, real-world transfer speed of an individual drive mechanism may be closer to 10mb/sec (check manufacturer's specifications at their web site before purchasing any drive). This transfer speed can be improved by configuring multiple drives into a Drive Array.

Drive Arrays use special software to combine multiple drives into a single volume (a volume is a portion of a hard drive that has been initialized for use with the operating system). On the desktop, you will only see one hard drive icon (or more if you partitioned the array into multiple volumes), but when this volume is written to, the file is divided up into pieces and multiple pieces are written to all of the drives simultaneously. By working together, the drives increase the total bandwidth that can be recorded, up to the total capacity of the Ultra2 SCSI interface. The advantage of this is that users can capture and play back higher quality video without dropping frames. The disadvantage is that if one of a group of striped drives stops working, all of the data stored in the entire array will be lost.

There are two pieces of drive striping software that work with Final Cut Pro at this time: Atto's ExpressRAID, and Adaptec's Remus. For further information about drive striping, see the documentation provided with these products.

Note: This article provides information about non-Apple products. Apple Computer, Inc. is not responsible for its content and mention of this product should not be interpreted as a recommendation by Apple. Please contact the vendors for additional information.