Page 27 - The Art of Designing Embedded Systems

14 THE ART OF DESIGNING EMBEDDED SYSTEMS

time savings up front. . . inevitably followed by hours or days of extra
time paying for the shortcut.
Never bypass the VCS. Check modules in and out as needed. Don’t
hoard checked-out modules “in case you need them.” Use the system as in-
tended, daily, so there’s no VCS cleanup needed at the project’s end.
The VCS is also a key part of the file backup plan. In my experience
it’s foolish to rely on the good intentions of people to back up religiously.
Some are passionately devoted; others are concerned but inconsistent. All
too often the data is worth more than all of the equipment in a building-
even more than the building itself. Sloppy backups spell eventual disaster.
I admit to being anal-retentive about backups. A fire that destroys all
of the equipment would be an incredible headache, but a guaranteed busi-
ness-buster is the one that smokes the data.
Yet, preaching about data duplication and implementing draconian
rules is singularly ineffective.
A VCS saves all project files on a single server, in the VCS database.
Develop a backup plan that saves the VCS files each and every night. With
the VCS there’s but one machine whose data is life and death for the com-
pany, so the backup problem is localized and tractable. Automate the
process as much as possible.

One Saturday morning I came into the office with two small
kids in tow. Something seemed odd, but my disbelief masked the
nightmare. Awakening from the fog of confusion I realized all of en-
gineering’s computers were missing! The entry point was a smashed
window in the back. Fearful there was some chance the bandits were
still in the facility I rushed the kids next door and called the cops.
The thieves had made off with an expensive haul of brand-new
computers, including the server that hosted the VCS and other criti-
cal files. The most recent backup tape, which had been plugged into
the drive on the server, was also missing.
Our backup strategy, though, included daily tape rotation into
a fireproof safe. After delighting the folks at Dell with a large emer-
gency computer order, we installed the one-day-old tape and came
back up with virtually no loss of data.
If you have never had an awful, data-destroying event occur,
just wait. It will surely happen. Be prepared.