In the Beginning, There Was Tape
August 30, 2012
By Brian Edminster
First in a series
In the beginning, there was tape. And if you’ve been around awhile, you remember it was on big reels about a foot across, was about a half-inch wide, and could have as much as 2400 feet of it on a reel. Yeah, they were heavy, too.
Data was recorded in parallel ‘tracks’ along the length of the tape. In this case nine of them, hence the name ‘9-track’ tape. At 800 bpi, that yielded a capacity of nearly 20Mb. Later technology allowed higher density, when 1600 bpi upped that capacity to about 120Mb. The last incarnation of 9-track was a whopping 6250 bpi — yielding nearly 1Gb of storage for a single reel of tape.
By comparison, anyone can get USB flash-drives that’ll hold 16Gb for $10 down at Walmart.
Very few, if any later model 3000’s (those that run MPE/iX vs. MPE/V) will even have a 9-track tape drive on them. And that’s a good thing. These 9-track tapes take up far too much physical storage space, and are far too slow to read and write. They might have been okay, back when disk drives were 50Mb, 120Mb, 404Mb, or even 570Mb (the capacities of the old HP 7920, 7925, 793x, and 7937 disk drives, respectively).
Unfortunately, a 2Gb drive is pretty much the smallest drive you’ll see on a 3000 these days, and larger drives are more common. This presents a problem: What do you do when it takes potentially dozens of tapes — and many hours — to do your daily backups?
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