On Sat, May 24, 2003 at 03:41:01PM -0400, Thor Lancelot Simon wrote:
> Backup to disk is nice, but you need to be a bit careful.  Disks are *not*
> designed to spin up and run nicely after being powered on, written to,
> and then powered off for a few years, so they're not suitable as long-term
> backup media.

I use RAID on my server.  In addition to this, I do daily / weekly / monthly
backups to a large disk which spins up for writing and then spins down again.
The disk specification say 50,000 start/stop cycles are allowed, so I'm not
going to worry about that.  Of course, I'm not going to power off the disk
for years.

In addidion to this, I copy the most recent daily/weekly/monthly files
to tape once a week.

> They are also significantly more mechanically complex than
> tapes, and if, for example, put in a safety deposit box that is then
> exposed to high heat or flooding, are a *lot* less likely to be readable
> whether with normal or heroic effort.

I don't think the tapes can take all that much heat, either..

> Tapes are not only designed for these purposes, they're tested to ensure
> that they're suitable for that kind of use -- accellerated and even
> actual aging tests, heat and water and mechanical wear tests, etc.  Tapes 
> can be re-spooled, spliced, etc; and I've successfully read 7-track
> tapes that were several decades old with no trouble at all once I got
> the 7-track drive working.

What was the bit density of such tapes?  I trust old disks and tapes more
than the new ones.  On an IBM XT clone we had a floppy drive which could
store data on cardboard (well, almost), but the new machines are always
having problems with floppies.  QIC tapes have never failed in my use,
but DAT tapes have - and I've had a DAT drive go bad as well.  I haven't
got a DLT drive yet.

  -jm