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Archiver > TMG > 2002-01 > 1009930217


From: "Cheri Casper" <>
Subject: RE: [TMG] A cautionary tale
Date: Tue, 1 Jan 2002 16:15:31 -0800
In-Reply-To: <DjQ6XHHqEkM8EAap@ntlworld.com>


Wow! That backup system seems almost complicated as TMG's learning curve!
When do you find time to do genealogy, mow the grass, shovel the snow, etc.?
Glad it works for you.

CheriC

-----Original Message-----
From: Wade Oram [mailto:]
Sent: Tuesday, January 01, 2002 3:07 PM
To:
Subject: Re: [TMG] A cautionary tale


In message <00ca01c1930d$085f3640$>, Caroline Gurney
<> writes

>d) don't rely on a cyclical process of, say, 5 backups. It often takes a
>long time before you discover an error (as Cheri has just found to her
cost)
>by which time the damage may well have affected a complete cycle of
backups.
>The only safe solution is to maintain a series of dated backups and, with
>CDs now so cheap, I have no excuse not to do this.

A fairly well used backup system uses tiered backups.
e.g daily, weekly, monthly.

For example, with 15 sets of backup media of whatever type:

6 for Daily Backups - Say Monday through to Saturday inclusive,
These are labelled according to the day and are re-used each month
4 for Weekly Backups performed every Sunday
These are cycled weekly omitting the week when the monthly (see
below) backup is performed.
5 for Monthly(?) Backups - performed every fifth Sunday.
These used every fifth Sunday and cycled each time.

Once a full cycle of this backup is in place, then you will know that
you have daily backups for the last week (the six Monday to Friday
backups + the last weekly backup), weekly backups for the last 5 weeks
(4 Weekly backups + the last monthly backup) and monthly backups for the
last 5 months.

Of course the number of months covered can be increased by increasing
the number of media in the monthly cycle (e.g. to 10 to give 20 media
sets used in total).

The other thing that ought to be done regularly is 'test the backups'. I
once had a faulty floppy disk which, although it would appear to write
perfectly OK, would not read disks at all. I have had similar problems
with tape drives. If, whilst a fault of this nature lay undetected and I
had been using only the faulty media for backups, I had had a disk crash
or some equally catastrophic fault which required me to go back to my
backups, then I would have lost all of my data. Not a pleasant thought!

With the above possibility in mind, when using the tiered backup
strategy, it would be worth using different backup media for each of the
tiers - e.g. Floppy disk/zip disk for the dailies,
CDRW for the weeklies and monthlies.

Tape was available as a third option for media then this could be used
for either the weeklies (I would think that CDR/RW is a more reliable
long term backup media - it is certainly cheaper than tape).

If an indefinite backup period is required then CDR could be used for
monthly backup.

--
Wade T. Oram


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