The Tao Of Backup: Parrot And Frog

Most people would agree that there aren't many activities more boring than taking a backup. This is one of the reasons why people suffer a data loss. However, even backups can be made enjoyable with a little imagination, as this story shows.


In 1989 I joined the Australian National railway company as a safety-critical software analyst on the Austrac train control project. Among other responsibilities, I had to establish a formal backup system for the VAX/VMS computer on which we performed all our formal analyses (using MALPAS). The computer had a system disk and a user disk, each of which could be backed up onto a single TK-50 tape. TK-50 System disk backups were required only occasionally because the system only changed during upgrades, but user disk backups were performed every day. We had a tape for each day of the week and for each week of the month and for each month of the year, and all these tapes were rotated and shipped offsite once per week.

A little thought made me realize that though the formal backup system was quite comprehensive, the biggest problem we would face if a disk ever crashed was determining with a high degree of confidence which was the most recent backup of all the backups made of that disk. I realized that we needed a way to identify the most recent backup tape of each disk so that there would be absolutely no confusion.

Parrot And Frog

So I went to a department store and bought a frog oven mitten and a parrot hand puppet. Each was just big enough to hold a TK-50 tape. I stored the most recent system backup tape in the frog and the most recent user backup tape in the parrot. This scheme ensured that if our user disk ever crashed there would be no question about which tape was the most recent. We'd just reach for the parrot! Similarly, if the system disk ever crashed, we'd simply reach for the frog.

The reaction of others to this new scheme was varied:

Terry Wardle Colin Turner Dave Keddie
The quality assurance officer, Terry Wardle, said: "This represents a major breakthrough in backup quality assurance." My boss's boss, Colin Turner, said: "Do you mean we actually own those things?" My boss, Dave Keddie, took it in his stride.

All in all, the reaction to the new scheme was positive, and the parrot and the frog sat happily in their locked cabinet, each satiated by the nourishing rectangular form of a TK-50 tape.

User backups were performed overnight and so each morning, upon arriving at work, I would remove the parrot's TK-50 and replace it with the one just written. This ritual evolved into the daily parrot stuffing ceremony in which a TK-50 was forcibly rammed up the parrot, accompanied by a painful squarking noise. After a while, this became a sound that the whole Austrac team expected to hear each morning.

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However, the area in which we worked was open plan, and after a couple of months of this, a guy from the Occupational Health And Safety department over the partition wandered over and asked "What's that funny noise we hear each morning?"

Thus the Parrot and the Frog not only provided instant unambiguous identification of the latest user and system backups, but also enlivened our mornings and provided a talking point among the locals.

Ross Williams

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