On 1/3/08 11:35 PM, Douglas A. Tutty wrote:
On Thu, Jan 03, 2008 at 05:10:59PM +0100, knitti wrote:
..
this is becoming OT, but I can't recommend storing HDDs as "real"
backup solution either. HDDs _do_ have bitrot, and one should at least,
say, once a year, verify that the *whole* disk is readable, ensuring that
sectors which are not yet completely unreadable get remapped. Vaulting
a DVD or a HDD for five years or more leaves you in both cases with the
real possibility of data loss.
If neither hard drives nor CD/DVDs are a good backup soluton, and
networking the backup to another computer's hard drive (which then
presumably also has the bitrot problem) isn't an option, and a DLT or
whatever tape drive is too expensive:
Then what other options are there?
CF, USB stick?
Just look at the specs!
Basically magnetics detoriate very slowly compared to about any other
technique used for storage.
However, for harddisks the bit's are not seriously read after write the way it
is done with good tape drives: A good tape drive verifies if a bit has enough
magnetisation to make it readable after 30 years (Exabyte specified it that
way). If the magnetisation is not enough for that the whole block will be
rewritten.
Since a tape is very robust compared to a harddisk, that's actually a very
complicated system with alligned heads, software and electronic parts that age
(diffusion of atoms!) so for backup nothing comes close to a good tape.
If you use a disk array for backup just consider it a test system but not as a
backup.
+++chefren
