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Re: [semi-OT] Data archiving (was Re: Query on adding a USB hdd)

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Douglas Allan Tutty wrote:
> On Fri, May 25, 2007 at 10:41:18AM +0200, Johannes Wiedersich wrote:
>> Douglas Allan Tutty wrote:
>>> No.  I figure a CD is good for at least a year.  Every year, I
>>> pull the two netinst cds from the bank, take an SHA hash and compare it
>>> with the written notes, then run something like cdck on them.  So far,
>>> my Woody CDs are fine.  Funny enough, so is my woody floppy set (the
>>> whole shebang set of 20 floppies) on Maxell floppies; needed for my 486
>>> that doesn't boot from CD or run an installer after woody's.
>> Wow, you seem to have a lot of spare time. How long does it take you to
>> perform all these checks?
> My backup set isn't that large so only an hour or so.

>> I do backups to usb hard drives. They have 40GB to 120GB and it takes on
>> the order of 1 minute / GB to diff -r them.
> So how often to you fsck -c the filesystem so that it attempts to read
> every block so that in turn the drive hardware can handle fading
> sectors?  Hard drives on a shelf aren't maintenance-free either.

My point was not that they are maintenance-free. My point was that both
backups and maintenance are much faster.

>> Considering lifetime and how often you're able to rewrite / reuse the
>> media, they are cheaper per GB than CDs/DVDs.
> True.  However, for a small data set (under 1 GB) the need for three
> copies means three hard drives.  Using a hard drive and rewriting over
> it means that you loose old archives.  

If you have 1GB of data and a say 40GB hard disk that means about 40
full backups on each. With incremental backups those would last much,
much longer.

For your three disks you'd have 120 full backups! Of course in the case
of failure you'd loose 40 of them, instead of loosing one unreadable CD,
but I consider checking 120 CDs for unreadable sectors etc. a nightmare.

Just my .02


NB: My backup system started out as DVD-RAMs, since those are said to be
more reliable than CDs/DVDs. I gave up on that scheme, when the data to
be backed up started to exceed 2 disks (and when my first DVD-Ram died -
probably related to the death of my laptop's multiburner). I now use
CDs, DVD-RAMs etc. for non-mission-critical stuff only.
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