Re: Storage: CD or DVD?
- From: "spamlet" <spam.morespam@xxxxxxxxxxxxxxx>
- Date: Thu, 24 Apr 2008 15:33:43 +0100
"Michael J. Mahon" <mjmahon@xxxxxxx> wrote in message
news:-padnZ9rYeq0EpLVnZ2dnUVZ_oaonZ2d@xxxxxxxxxxxxxx
Steve H wrote:
Thanks for the up to date tips.
So to get this clear:
Nobody seems to be saying we need to keep 'permanent' back ups on
'traditional' (still new to me!) media discs any more?
Everyone seems happy to put as many files as will fit on a particular
storage device, on that device?
Everyone seems happy that they will always be able to recover files from
that medium in the future?
No matter what medium you choose, you will need to guard against
obsolescence by re-copying to new media from time to time.
At least hard drives are well known to be stable for many years of
storage, while their are many cases of writable optical media becoming
unreadable after relatively short periods. It may be marginal media
or marginal writing, but the problem nevertheless exists, and is not
always found by verifying the write soon after writing.
SATA hard drives have an interface which is relatively new and can
be expected to have a long life--at least ten years, so it would seem
to be a good choice for a backup medium for the next decade.
Ten years down the line, if SATA seems about to be replaced by a new
drive interface, the drive can be copied over to a newer (100 times
bigger) drive very quickly and with almost no trouble.
Much the same can be said for external drives with USB2 or FireWire
connections. Though their speeds will be somewhat slower than the
newer SATA links, the proliferation (of USB2 particularly) ensures
that it will not go away for many years.
Compare that to re-copying, say, 100 DVDs (about 500GB) to Blu-Ray II,
or whatever the next optical standard will be. Copying 100 disks will
be a lot more trouble and have a much greater liklihood of errors than
simply doing a single drive-to-drive copy.
The key to durable storage, as noted earlier in this thread, is multiple
copies not all in the same place (or even locale--after all, there are
regional disasters). All copies must be periodically checked for
deterioration and eventually re-copied to newer media to ensure that
they will remain usable.
It's best to make the inevitable re-copying to new media/interfaces as
fast and simple as possible, so that it won't be put off too long.
'Flash' drives/'sticks' are not safe?
(I once saw a 'Braniac' programme where they tried to destroy a number of
different media by doing things like shooting cannons and flame throwers
at them. Even when it appeared to have been smashed up, they still
managed to get data back off the flash drive - in a laboratory
admittedly!)
Flash drives are safe for the short term, but they store data as tiny
electrically isolated charged regions in silicon chips. The leakage of
these charged regions is not zero, and rises with temperature. Further,
ionizing radiation (like cosmic rays) are a continuous source of local
discharge (usually covered by error correcting codes, until there are
too many errors). Magnetic drives are not subject to degradation from
cosmic rays.
As a result, I would not consider flash memory stable for more than a
a decade. And, of course, the interface to the flash memory (SD,
CompactFlash, etc.) is a moving target and subject to obsolescence in
the same timeframe.
So, at best, flash media need to be re-copied at least as often as
hard drives, and their storage cost is at least 25 times as expensive
as good hard drives, and their capacity is 100x-200x smaller, meaning
that one hard drive would store 100-200 flash drives. This translates
into a considerable difference in effort in re-copying when the time
comes.
If, at some point, the unit capacities and costs of flash media should
approach or overtake magnetic hard drives--a situation that is unlikely
for at least the next decade--then this tradeoff might eventually shift
toward flash media.
Additional points:
As capacity rises, is JPG on the way out too?
A factor of ten saving in storage space with negligible losses for most
purposes (think snapshots) virtually ensures that lossy compression will
always be the norm. It already is for video--there is no uncompressed
digital video.
A newer compressed photo format may emerge, but it won't be because we
found a way to increase compression another 4-fold--it will be because
we found a way to improve dynamic range by a factor of ten without
adding significantly to file size. And you can be sure that it will be
"backward compatible" with JPEG. Sheer volume provides real insurance.
If a wonderful file format should be invented, then there will be
programs to automatically convert all older files to the new format
in the process of re-copying them to new media.
Should I be saving pics as TIFF (JPG2000? Raw?) to make best use of the
new space, and only converting to JPG/PNG for emailing?
It depends on how much you value relatively invisible but potentially
useful information in your photos. If they are for "casual" purposes,
then medium-high quality compression will never be a cause for regret
and will save you a factor of 10 in storage space, copying time, etc.
If some of your photos have "archival value" that is likely to lead you
to enhance them further at some later time, then an uncompressed format
may be appropriate.
Presumably it is faster/more reliable to connect any new hard drive via
cable than wireless?
It seems likely that wired connection will always deliver substantially
more bandwidth than wireless connections, unless something discontinuous
happens in the networking space.
Network storage?
A fine solution for your local network, but quite slow for uploads if
the storage is accessed over the internet. Most private internet
connections have upload speeds limited to a few hundred kilobits per
second--about a factor of ten slower than their download speeds.
And download speeds of, say, 5Mbits per second, translate to about
0.5MBytes per second, which is 20-50 times slower than a copy
from hard disk to hard disk.
If you have a network storage server on your local network, and it
runs at 100Mbits per second (likely for a wired connection), then
copies over the network can be expected to reach 5-7MBytes per
second, still 2-5 times slower than a disk-to-disk copy.
(For example of why I want to 'get this right for once': I had a habit of
compressing old floppy discs, and, only by chance discovered that the
ability to mount them went out with W98, before chucking out my W98; now
XP is on the way out; my email on OE seems to be on the way out - and
hotmail too!; I'm only a quarter way through copying my video tapes to
DVD - how nice it is to have access to old programmes with no channel
'water mark' and with the credits not shoved to one side at the end! -,
but now expect I will have to do it all over again from DVD to whatever,
before I even finish... Presumably 'High Definition' means that soon
ordinary DVD will be obsolete because no programmes will fit... Nice to
know that storage capacity is rising so rapidly but so it seems is
'losage capacity!)
Progress is, indeed, a two-edged sword. ;-)
The biggest problem, as you have noticed, is large numbers of tapes,
discs, flash drives, etc., since it makes re-copying slow and usually
manual.
Having "all your eggs in one, huge basket" (and copied to another huge
basket, of course) is the solution to this problem. Re-copying is then
as simple as making one connection and running a copy program.
Of course, if your total storage needs exceed 1TB, then you will need
multiple hard drives--but *many fewer* of them than of any other, less
capacious media!
Note that a 1TB drive stores about 40 Blu-Ray disks, and a Blu-Ray
burner and 40 recordable Blu-Ray disks will cost over $500 for at least
a few years, while a 1TB drive will cost less than $300 (and dropping
fast) and will greatly ease copying, handling, and storage for the next
decade. In a couple of years, the same price point will buy a 2TB
drive.
Liked the bit about hard drives 'parking their heads' these days: I am
extreemly lucky to be writing this on a laptop where all the info and
operating system was almost permanently 'parked' after the owner trod on
it. Amazingly, I risked opening the drive, and found that a little manual
rotation got it moving again!
Congratulations!
I hadn't thought of actually putting another hard drive inside the pc
enclosure. Ours is a dell Optiplex desktop model, which does not seem to
have spare slots like the tower versions do. Are there any 'good ones'
you would recommend that might fit?
The price-performance "sweet spot" is 3.5" hard drives. The older ATA
parallel interface is becoming obsolescent, while SATA is rapidly
becoming the universal hard disk interface.
If your desktop does not have a spare 3.5" drive bay (all but the very
compact models do), then you may need to use an external USB2 drive.
This may slightly reduce your copying speed (depending on your computer)
but will serve very well. It will have an external power supply, which
you should ensure is safely connected before use--power failure is an
inconvenience to avoid, though NTFS is a journaled file system and can
recover from interrupted actions.
Virtually all desktop motherboards have dual hard disk ports, either
two separate SATA ports or two daisy-chained ATA ports. If you find
that your computer can accomodate another internal 3.5" drive, you
should pick one with the appropriate interface.
When the time comes to upgrade, your new machine will inevitably have
SATA hard drive ports, and it will very likely have at least one ATA
port for its optical drive(s) (though SATA is becoming the standard
for optical drives, too). You can arrange to copy your ATA drive(s) to
your SATA drives by temporarily connecting your ATA drive(s), one at a
time, to the spare ATA port and then "dragging and dropping" its files
to a subdirectory of the new drive (where it will usually occupy only
a small fraction of the available space).
I just bought a nice 'dj' storage box for my CD/DVDs too...
That can be a handy way of automating the copy of lots of discs--
assuming that there is a copy program that will sequence through
them...
Keep em coming.
Kind regards,
I hope it's helpful. ;-)
-michael
Michael!
This is one of the best bits of writing I have seen in these groups.
I am sure I did not deserve such a thorough and thoughtful response!
Your advice will be going straight to my desktop and passed on at every
opportunity.
Thank you very much indeed.
And so on to checking what exactly is in our pc box...
Cheers :-)
S
.
- References:
- Storage: CD or DVD?
- From: spamlet
- Re: Storage: CD or DVD?
- From: Steve H
- Re: Storage: CD or DVD?
- From: Michael J. Mahon
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