Article, July 2012
Disks - What would our computers be without them?
By Phil Sorrentino, President,
Sarasota PCUG, Florida September 2011 issue,
Sarasota PC Monitor
president (at) spcug.org
Well, they’d be Tablets, or Smartphones, neither of which have disks as integral parts of the hardware. The Disk or Disk Drive usually refers to the component of the computer that typically stores large amounts of data. Storage can be, only readable, or readable and writeable (or recordable). There are two types of Disk Drives that are usually part of a Personal Computer, Magnetic and Optical. Magnetic drives are typically readable and writable. Now-a-days, magnetic drives store in the hundreds of Gigabytes (1 Gigabyte = 1,000 Megabytes). Optical drives are either readable (ROM) or recordable (RAM). Optical drives come in three different storage sizes, CDs (Compact Disks) which hold 700 Megabytes, DVDs (Digital Versatile Disks) which hold 4.7 Gigabytes, and BDs (Blu-ray Disks) which hold 25 Gigabytes.
Magnetic Disks or Magnetic Disk Drives, or Hard Drives, (can any of you remember the term, Winchester Drive), are at the very core of the personal computer. For those of you who remembered “Winchester”, the original IBM PC didn’t even have a hard drive. It only had one or possibly two 5 ¼ inch floppy disks. Remember the a: drive? And I bet there are only a few of you who ever had a b: drive (the second floppy).
The hard drive came along around 1983, with the IBM PC/XT, and was assigned as the c: drive. Then came Optical drives, the CD ROM (around 1985), and the recordable version, the CD RAM (around 1990). These were typically assigned as the d: drive. Finally, The DVD came on the scene with backward compatibility with CDs. The DVD ROM appeared around 1995 and the DVD RAM around 1998. DVD equipment is backward compatible meaning they can use DVD or CD media (the actual disk). BDs are relatively new, coming on the scene around 2009. The BDs come in BD R which is recordable only once, and BD RE which is recordable and re-recordable. BD equipment is backward compatible meaning they can use BD, DVD or CD media.
Specifying a magnetic disk drive is pretty straightforward. The only variables are the storage capacity and the speed. Today, typically, the speed is 7200 rpm. Although there are some older units around that rotate at 5400 rpm, and there are some fast drives that are running at 10,000 rpm, but they are the exception. So, the defining item is the storage capacity, which today runs from 100 Gigabytes to a few Terabytes (1Terabyte = 1,000 Gigabytes). Once the manufacturer is chosen and the speed and storage is picked, the job is about done. The only other factor is the interface. SATA (Serial Advanced Technology Attachment), today, is the preferred interface, but only if your computer has the hardware to support it. The older interface is called IDE (Integrated Drive Electronics), and sometimes called PATA (Parallel Advanced Technology Attachment).
Specifying Optical Disks is somewhat more involved. The first decision is the storage capacity. Today, DVD drives are probably the most cost effective (the best storage per dollar). Because DVD drives are backwards compatible they can be used with DVDs or CDs. BD drives are currently quite expensive and will probably not be found on most personal computers. BD drives will probably be around $100 in contrast to about $35 for a DVD drive. If you have only one DVD drive on your computer, it should probably be a drive that is capable of writing disks as well as reading them. If you have the luxury of two optical drives (probably on a desktop), one can be just readable, which will keep the cost of the pair to a minimum. Optical Drives that are capable of writing are sometimes called “Burners” because the writing operation uses a laser to “burn” data spots on to the disk media.
The round 120 millimeter (4.7 inch) disk that you insert into the Optical Disk drive is called the disk media. The media type should match the Disk Drive type, meaning that you typically use CD media in a CD Drive, DVD media in a DVD drive, and BD media in a BD drive, although there is backward compatibility. For Optical disk media, readable means that the disk can be written only once and then read many times; read/writable means that the disk is readable and can be written and re-written many times. CD disk media comes in two types, CD-R (readable), and CD-RW (read/writable). Unfortunately, DVD disk media comes in two disk varieties DVD- (the dash variety), and DVD+ (the plus variety), as well as being readable or read/writable. The good news is that, now-a-days, all drives can use either of these varieties. (Although, I have heard that some people prefer the DVD- for movies. They have reported better results with that variety for movies that were created on the computer DVD disk drive and then played on their living room DVD player.) So, typically, DVD Drives can accommodate DVD-R (read only), DVD-RW (read/writable), DVD+R (read only), or DVD+RW (read/writeable) media. This is usually indicated by stating that the drive can be used with DVD±R disk media (readable), or DVD±RW (read/writable) media. Fortunately, BD disk media does not have the same problem. There is only one variety for BD disks, BD-: BD-R (readable), and BD-RE (read/writable).
Now that we have chosen an optical disk drive based on storage capacity, and we now know what media we can use with the drive, the last thing to look at is the speed of the drive. For Drives that only read, this is not really an issue because the read speed is typically faster than any of the writing speeds. An Optical Drive writing speed is specified as #X. Currently, for DVDs, # is a number between 1 and 52. This number indicates the speed relative to the original disk writing speed. So an Optical Disk capable of writing at 12X would write a disk 12 times faster than the original writing speed. The original writing speeds for the different Optical Drive types are: CD=.15Mbps; DVD=1.35Mbps; BD=4.5Mbps. So a 12X DVD Drive would write data at 12 times 1.35Mbps, or 16.2Mbps. Optical Disk media is also rated for writing speed in the same way. When you buy Optical Disk media it is always good to buy media that is at least as fast as your drive so that you take advantage of your drive's maximum speed. If it is not at a great expense, faster media will probably give you better, although not faster results.
Disk drives, magnetic and optical, give the computer the ability to store and access enormous amounts of data. Without these devices we might be confined to only using the “cloud” for our storage (do any of you remember “mainframe” computing?). But, even with these devices, they may be the direction personal computing is taking, anyway.Click here to return to top