In the message dated: Mon, 24 Sep 2007 11:04:00 EDT,
The pithy ruminations from Bob Hetzel on
<Re: [Bacula-users] Backup to disk AND tape> were:
=> The reality is that if you really need reliable data for 10 years you're
=> probably stuck with technology like paper, optical media (choose wisely
Paper? True, it's about the best archival media that we've got...however,
the information density is too low to be practical for most data formats. I've
yet to see a usable way of rapidly and reliably converting arbitrary data to
--and from--machine readable symbols on paper. I guess that the
Data Matrix encoding from Siemens has sufficient density (theoretically storing
about 37GB per US Letter page, but practically many orders of magnitude
smaller)/
However, I'd argue that the issues you raise with reading tapes--having the
hardware and software to access the data, rather than deterioration of the media
itself--would also be a major problem for any high density storage printed on
paper. I think that microfilm would be a better answer, with a very simple
binary-data-to-text encoding (UUENCODE, for example).
=> as many of these formats are gone too), or online hard drive space that
=> you'll be continually checking and carrying along with each upgrade (and
=> backing up with all your regular fulls). All have their own major
=> drawbacks. The benefit to online hard drive space is that new data
=> needs grow so fast that in many cases it's not that much more expensive
=> to keep the old stuff around--for instance... 20 years ago 100GB of data
=> was not available in one storage system. 10 years ago it was a lot but
=> quite pricey. Now it's about the smallest hard drive you can buy new.
While that does reflect the change in drive space per unit or per cost over
time, that's not in and of itself an advantage of hard drives. If I purchase a
drive today and put data on it with the intent of keeping that data for 10
years, I've still got to be able to access the drive that I just purchased,
even if 5 years from now new drives are cheaper and have higher densities. The
same issues with bus connections, drivers, etc. still apply. We're already
seeing this with machines that don't support PATA drives, and with pulling data
off older SCSI drives.
=>
=> The odds that you can locate a working tape drive of any current (2007
=> hardware) type and adapters to plug it into 10 years from now (2017
=> hardware) aren't good the way things are moving. Not only will you have
It depends on what level of technology you are considering.
=> to worry about hardware--is PCI still going to go the way of the ISA bus
=> by then?--but drivers for old adapters on the OS after the next OS are
=> quite possibly going to be a problem--there's tons of useless adapters
=> out there now where manufacturers went out of business before updating
=> their NT 4.0 drivers to work with XP, Server 2000, and Server 2003, so
=> even if you save both the tape drive and the adapter who's to say the
=> adapter will have a spot to plug it in and a driver you can load.
Absolutely, if you're dealing with low-end (small office/consumer) hardware.
For this discussion, I'd immediately rule out any device that has it's own bus
adapter and drivers.
I'm very, very confident that a 4Gb/s fibre-attached LTO3 or LTO4 or AIT5 drive
purchased today will be usable on a SAN in 10 years. Of course, that might be a
64GB/s SAN, and I might not be able to purchase any more LTO4 media, and I may
need to keep the drive that I purchase in 5 years in order to read the tapes I
write today, and my current drive might not be able to write to my 10 year old
LTO4 media...but I believe that I'd be able to read the data. For example, AIT
manufactureres have a very firm commitment to generational compatability. AIT5
(released in 2006), for example, is read/write compatible with media back to
AIT3 (released in 2001). I believe that the standard says that AIT"n" will be RW
compatible with AIT"n-1", and read compatible with AIT"n-2".
=>
=> With regard to 30 years I can almost guarantee problems with just about
=> any electronic removable media. While it's true that you can probably
Yep.
[SNIP!]
=>
=> In summary... backup software is extremely important for disaster
=> recovery but should not be considered for long term (5+ years, possibly
=> even less depending on what you need it for) storage needs in my humble
=> opinion.
=>
[SNIP!]
I agree, in that backup is not entirely the same thing as "archive".
Mark
----
Mark Bergman [EMAIL PROTECTED]
System Administrator
Section of Biomedical Image Analysis 215-662-7310
Department of Radiology, University of Pennsylvania
http://pgpkeys.pca.dfn.de:11371/pks/lookup?search=mark.bergman%40.uphs.upenn.edu
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