On Sat, Jun 01, 2019 at 08:29:02AM +0100, Ed wrote:
> On 2019-05-31 23:56+0000, Hugo Mills wrote:
> > I started out writing CD-Rs about 15 years ago, migrated to DVD+R,
> > and then to BD-R. I'm considering LTO-6 as the next migration, despite
> > the poor economics w.r.t. BR-R at my kind of scale.
>
> What is the data integrity on optical media over ten or more years? I
> have some CDs from 1990's era (silver) and starting to go mouldy. Many
> of my writable CDs have lost their film, so useless for long term data
> retention.
It depends on the quality of the media. I've seen some that didn't
last more than the time it took to put the new-burned disk into its
case. (Seriously -- they were practically see-through). I've gone 5-8
years on mine without obvious data corruption. I believe it's possible
to get media which are intended for long-term storage, and they're
reputed to go up to 100 years, but those are going to be spendy.
Personally, I'd refresh the media at least every 10 years or so for
"bog standard" (but reasonably reputable) disks. I used to use TDK,
but I haven't seen a TDK optical medium for a few years -- I think
they dropped out of the market. I'm now on Verbatims.
> LTO on the other hand should span multiple decades without issue. If I
> remember correctly, the tape should be forward compatible with drives
> (not sure if there's a maximum number of iterations here, but I'd hope
> not).
With a drive of generation N <= 7, you can use tapes of no earlier
than generation N-2 for reading, and N-1 for writing. For N=8 (the
latest), you can only use tapes no earlier than gen N-1, for reading
or writing.
> You could regularly export ZFS mirrors if you work spinny disks out to
> be lower cost than LTO.
>
> Remember to off-site one half of the mirror.
Yes, this is an important point.
Hugo.
--
Hugo Mills | I went to a fight once, and an ice hockey match
hugo@... carfax.org.uk | broke out.
http://carfax.org.uk/ |
PGP: E2AB1DE4 |
