There are a few attributes of hard drives to consider. The first and most obvious is the size. The larger the disk, the more music you'll be able to store. Like RAM, this number is expressed in GB or terabytes (TB). A terabyte is 1,000 GB. How big should your drive be? Buy as much hard drive as you can afford. More is definitely better.
The next critical factor in a hard disk is the rotation speed. A hard disk spins in the same way a CD does. The speed at which it spins is measured in revolutions per minute (RPM). The higher the speed, the faster the disk can access its data. Why is this important to you? Faster disks equal higher track counts in the software you use. If you have a fast CPU with tons of RAM, a slow hard drive will still limit you. The faster, the better. You will also find recommendations for hard drive speed listed on audio software manufacturers’ lists of recommended hardware.
Digital audio requires a good deal of storage space on your hard disk. Every minute of every track you record takes up many megabytes of space. As the quality of the recorded audio improves, file size increases as well. A typical five-minute song recorded in eight tracks with minimal effects can use 320 MB of storage space. This is why large hard drives are crucial.
The last factor is seek time. Seek time is how fast the data on the disk can be accessed. Seek time is measured in milliseconds. The lower the seek time, the better. You'll find that many drives average between 8-10ms of seek time. The lower, the better.
I'll Take Two
Chances are your computer came with only one hard drive, and this works fine. You can record and store files on a single hard drive. However, it's preferable to have a second hard drive dedicated to audio file storage. Why is this? Simply put, if you have one hard disk, the computer has to use the disk for running the operating system, running any open programs, and recording huge music files. This is a bit much to ask of just one disk. Your track count will always suffer by using one drive.
One Drive Can be Okay
You don't have to run out and buy a second hard drive right away, however. It's best to start out with one drive and see if you overtax the machine. Much depends on the number of tracks you work with and how many are audio versus MIDI. If you run into problems, use the advice from the previous section and get a second drive to increase performance and reliability.
Internal or External?
If you opt for the second drive, you have a choice: internal or external. Some computers won't accept a second internal drive, so that choice is made for you. Both get the job done, so it really comes down to personal preference and what your computer can handle. The only advantage of an external drive is that you can take it from computer to computer. If you collaborate with other home studio users, this could be a big plus. USB and FireWire are popular choices for external drives. Many users still swear that FireWire is more reliable for audio than USB, plus it's worthwhile to note that Digidesign does not recommend or support USB drives.