Re: Why can't computers be simple?

On Fri, 22 Jun 2007 17:27:33 -0400, Ian Gregory wrote
(in article <5e2t65F36r2uhU1@xxxxxxxxxxxxxxxxxx>):

On 2007-06-22, Jolly Roger <jollyroger@xxxxxxxxxxxxxxxxxxxxx> wrote:
On 2007-06-21 14:43:35 -0500, Mark Conrad <noneof@xxxxxxxxxxxxxxxxxx> said:

With commercial backup app's, one is never really certain whether
something will be backed up or not, until one finds out the hard way
that something of value was not backed up.

Bull***.

Partly. The main error as far as I am concerned is the "commercial"
qualifier. All backup systems have potential bugs that could result
in data loss, whether commercial, open source or homebrewed.

Apparently there is a big US car company that lost 100 man-years
of design work due to storage failure.

Ford, right? IIRC they had a bad tape drive. The failure wasn't anything to
do with the software, but with the hardware. If you're referring to the
incident I think you're referring to.

They were not too worried
because it was backed up, but then they found that all the backup
tapes they had been religiously making were blank!

There can be a certain ammount of checking built into the backup
system, for example writing data in blocks and reading back what
was written before moving on to the next block. Ultimately though
you should really do restore-drill like you do fire-drill. Pick
a randomish moment and imagine that you accidentally deleted a
file (rename it temporarily to something else). Now, can you
recover it from your backup system?

Ian



SOP _is_ to periodically restore a file or a folder or even an entire volume,
just to see what happens. At least, that was how it was written up in the
manual for the first set of backup software I ever used, lo! these many years
back. I remember 'cause, as The New Guy, it was _my_ job to make test
restored files. According to the manual, the reason for doing the test
restore was to make sure that you didn't have either hardware or media
failures.

Mostly, though, you guard against media failures by doing more than one
backup, to different types of media where possible. And you guard against
hardware failure by using more than one backup device. If you're guarding
against media failure by using two different types of media, you're
_automatically guarding against hardware failure. If Accounting objects to
spending the money for two types of backup, put out in writing the reasons
why you need them. And wait for a media failure, which _will_ happen if you
have enough backups. Or wait for a hardware failure, which also _will_ happen
if you use the same hardware long enough. Or if you actually believe the bumf
on the box; AIT 4 tape drives, for example, are allegedly compatible with AIT
3 tape, according to Sony, anyway. No they're not. And anyone who wants to
can test this out. Do it with something you can afford to lose. I can tell
you stories about tape, and assorted types of optical media, and hard drives.
There's a reason why my primary backup system at home are hard drives...
which are unmounted and shut down as soon as backup is complete; after all, a
MTBF of 50,000 hours includes tomorrow, and by definition half of the drives
are going to fail _before_ 50,000 hours of operation... And why if I put
something on CD or DVD I put it on _several_ CDs or DVDs. Just in case.

--
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