Storage Media Guide

As a digital photographer, I’ve come to appreciate the differences between storage media. Having to both permanently and temporarily store thousands of critical files will do that.

Undeniably, the magnetic hard disk has been the most reliable in terms of long-term storage, and yet the most volatile. It’s simply too easy to delete files by mistake. Only until recently has the problem been pretty much solved, at least in the Macintosh world. Time Machine, the OS-Native backup utility included with the Mac OS, backs up your files automatically, every hour, and maintains backups of files that were deleted. It does so very intelligently, only backing up the files that have recently changed, and only deleting previous backups if you run out of room, by which time you probably will have discovered the data you accidentally erased and and restored it. Yet it maintains this information in a user-friendly timeline format. However, this only solves the problem of your “live” or “online” storage. Eventually your hard disk will fill up, and you’ll have to find a medium on which to archive your information.

To this end, several forms of removable read/write magnetic storage media evolved. The 5.25" and 3.5" floppy disk and Iomega Zip and Bernoulli disks all employed flexible, magnetically encoded media with moderate capacity. The higher capacity Iomega Jaz, and SyQuest EZ135, EZFlyer, SyJet, SparQ and Quest drives employed rigid magnetically encoded media more like an internal hard disk. Thus they offered greater capacity and speed. All however were prone to reliability issues due to contamination by magnetic fields or dust.

Recordable optical media, which started out as the MO or Magneto-Optical disk in 1985 solved this problem. It contained sectors just like a hard drive, and as such, individual files could written and erased at will. It was very reliable, but also very slow. It used a hybrid of optical technology to erase and write data, and magnetic technology to read it. With the wide availability of CD-ROM drives, Recordable optical media eventually evolved into a purely optical media, the CD-R and CD-RW.

In this world of flash memory, aka “thumb” drives, the optical disc still reigns superior in archival storage. It’s inexpensive, reasonably stable, and unless you’re using rewritable media, cannot be accidentally erased. If you use good quality media, take your time to burn the disc at a reduced speed, and store it wisely, you will wind up with a volume that will last many years. If you develop a system of indexing the many discs that will result, you’ll be able to find data quickly.

The optical disc is now available in many different formats. Although not a sectored, read/write technology (a CD or DVD contains a single, spiral track indexed through a table of contents created when the disc is burned) advances in technology have made it fast and reliable.

Now, wrap you mind around this.

Optical storage in not a new concept. The means of analog optical storage was first invented in 1825 by Joseph Nicéphore Niépce. The 1920s saw widespread use of microfilm as an archival storage medium. By contrast, the optical disc is a digital optical storage medium. The difference is, microfilm and microfiche do not require digital to analog decoding in order to be read. Digital encoding does.

Surpassing the Optical Disc for convenience and compatibility, but not reliability, is flash memory. Flash memory is composed of microscopic capacitors, as opposed to the transistors used in conventional memory. This means that flash memory is theoretically prone to longevity issues. Failure of these capacitors after data is written will render it ureadable. Therefore, it is suitable only for short-term storage. That said however, the solid-state nature of flash memory with no moving parts increases its reliability over magnetic media, and many have reported that flash media has survived a wash and dry cycle when accidentally left in a pocket.

The advent of the flash drive employing a USB interface has launched it far ahead of any other media requiring a separate drive to be read, and it capacity is many times more than any magnetic, magneto-optical or optical storage media introduced to date.

Here’s a guide to which format to use for a given purpose:

Media	Capacity	Purpose
External Magnetic Hard Disk	Up to 10TB and beyond	High-capacity, short to long term archival data storage or backup.
DVD+R DL, DVD-R DL	8.5GB	High-capacity, long term archival data storage.
DVD+R, DVD-R	4.7GB	High-capacity, long term archival data storage.
DVD-RW	4.7GB	High capacity, mid-term data storage or backup.
CD-R	650MB, 700MB	Moderate-capacity, long term archival data storage.
CD-RW	650MB, 700MB	Moderate-capacity, mid-term data storage or backup.
USB Flash Drive	128MB-32GB	Low to high capacity, short to mid-term data storage or backup.
Secure Digital, CompactFlash, MemoryStick, MultiMedia, SmartMedia, xD-Picture Card	32MB-32GB	Low to high capacity, short to mid-term data storage or backup.