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Cost of DVD as data storage versus HDD (UK)



 
 
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  #21  
Old October 14th 04, 01:49 PM
J. Clarke
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Daniel James wrote:

In article , GSV Three Minds in a
Can wrote:
Don't cross-post to so many groups (many people kill anything
crossposted to 3 places, on the assumption that if the OP doesn't know
which group it goes it, it won't be of much interest in any of them).


aside
.. and in doing so avoid a huge amount of junk and a few interesting
discussions.

I must say I'd find it "challenging" to dream up a post that could
legitimately be posted to more than about five groups, but I don't think
four is necessarily out of order.

The OP selected four groups for a posting which seems to me to be
reasonably on-topic for all of them ... except possibly uk.comp.homebuilt
(which is where I'm reading it, as it happens) where it is a common enough
subject fr discussion, if not strictly on-topic.
/aside

Back to the question .. cost per byte is not an interesting metric for
backups, unless you include the cost of making the backup and the cost
of securing it against whatever disaster you are backing up against.


.. and, perhaps more importantly, the value of the data.

People gaily make disk images of their whole system, but unless you can
produce =identical= hardware this is of no use at all if your original
system is stolen, ...


That's a good point, and one that's not made often enough.

If you have the original applications on CD, or you can buy
new copies from MS, there isn't much point in wasting time and money
making copies every day/week for the rest of your life.


Also true. One might think -- especially give the time it takes to install
some large applications -- that backing up once after an install would be
a time-saver, but in general when software is installed (on Windows, that
is) it sets a cartload of registry entries that aren't easily backed up in
isolation. Backing up the whole registry isn't useful if disaster forces a
change of hardware (which will mean the system-specific parts of the
registry will no longer apply). Reinstallation is really the only safe
choice.

That registry is a pain in the proverbial, sometimes.


For a large system a product such as Novell Zenworks can help deal with
this--it takes a snapshot of the system before and after an application is
installed, and after you clean up the excess baggage (something always
seems to change that has nothing to do with the installation) you can
quickly reinstall or install to other systems from the snapshot. It's also
very nice for figuring out what actually _did_ happen during the
installation when the installation hoses something.

In a perfect world, RAID1 or RAID5 for continuous up-time even if a disk
crashes (which they are increasingly prone to do), tape backups of
anything that can't be reproduced easily .. daily ones, or weekly, or
whatever turns out to be the best tradeoff between 'cost of prevention'
and 'cost of recovering what you hadn't prevented being lost'.


Good advice. Add to that that the daily/weekly backups (on whatever medium
they're made) should be test-restored so that you can be sure that they
*can* be restored, in the event of disaster (and that you've backed up
everything you need). Keep a spare device that can read the backups, in
case the original fails. Having a good tape backup regime is no good if,
when you need to restore some old data, you find that the tape drive is
knackered and that that type of drive is no longer available.

You can spend a fortune on backup and still not get it right -- and you
certainly can't get it all right without spending a fortune. How much you
do spend must depend on the value of the data.

Cheers,
Daniel.


--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
  #22  
Old October 14th 04, 06:46 PM
Dorothy Bradbury
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MOD/DVD-RAM (similar technology) is very good for smaller backups
with high reliability requirements. Also for long-term storage.


Indeed - I use MO for just that reason, however now also use DVD-RAM:
o MO media QC has blips - a few too many
---- Sony 540MB 3.5" -- block errors on new disks
---- Fujitsu own 3.5" -- block error on *same place* on every disk - factory format
error
o DVD-RAM has been ok - and is higher capacity
---- 10 will get a two-sided 9.4GB disk
---- LG-4082B will write to them once removed from the caddy

Since I use DVD-RAM once-only for archive the removal from the caddy is minor.
If bothered use cotton gloves - whatever - it's 15x MO capacity for the same price.

MO is best for the most critical backups
o It was designed for data reliability from the ground up like DLT
o It is not a converted audio standard like helical scan DAT, or DVD

However, the "real" MO systems are based around the 5.25" form-factor:
o New blue-laser ones offer a migration path to very high data capacities
o The 5.25" form factor is relatively well proven in medical/mil/industrial

For the most part, DVD-RAM offers a good half-way house:
o Reliability is good - it is Phase-Change unlike DVD+/-R & has better error correction
o Drives are cheap - so having 2 different branded drives isn't impossible (or suppliers
:-)
o Disks are cheap - 9.4GB can be had for just 6.99, sealed, a bit more elsewhere

MO is ~200 drive & ~10 media for 1.3GB v ~60 drive & ~7 media for 9.4GB.
Critical stuff is best on MO, but with those media errors I think it's forget about
decades:
o Yes, backup media can last a long time - DVD-RAM probably, MO most probably
o However, it is perhaps more economic to keep changing technology every few yrs
---- because technology will offer more capacity, perhaps more reliability for less cost
---- that is particularly so with media cost as archives grow - eg, DVD-RAM v MO

Agreed - many people backup to DVD-RAM or HDs "incorrectly"
o They simply drag-n-drop files - directory is there, so it must be ok
o Better to use a proper backup tool - that actually does a proper compare
---- altho even XCOPY can be forced to do a verification as I recall
---- on DVD-RAM that might be an exercise in s-l-o-w-n-e-s-s however

If HDs are used, I prefer a "micro-PC" converted to NAS - with a few scripts to check
the data integrity progressively to another identical machine working in parallel. That
need not be particularly expensive - Mini-ITX snails don't cost much, recycle some of
the older 1U PSUs, make/re-use a case, whatever. Match solution to data criticality.
--
Dorothy Bradbury


  #23  
Old October 15th 04, 02:27 AM
Arno Wagner
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In comp.sys.ibm.pc.hardware.storage Dorothy Bradbury wrote:
MOD/DVD-RAM (similar technology) is very good for smaller backups
with high reliability requirements. Also for long-term storage.


Indeed - I use MO for just that reason, however now also use DVD-RAM:
o MO media QC has blips - a few too many
---- Sony 540MB 3.5" -- block errors on new disks
---- Fujitsu own 3.5" -- block error on *same place* on every disk - factory format
error
o DVD-RAM has been ok - and is higher capacity
---- 10 will get a two-sided 9.4GB disk
---- LG-4082B will write to them once removed from the caddy


Since I use DVD-RAM once-only for archive the removal from the caddy
is minor. If bothered use cotton gloves - whatever - it's 15x MO
capacity for the same price.


Well, not quite. The last time I bought 3.5" 640MB MOs, I paid 5 Euro
for each. The cheapest DVD-RAM I find is the same price for 4.7GB.
That is a factor of 7. Still signifficant if you do large backups.

MO is best for the most critical backups
o It was designed for data reliability from the ground up like DLT
o It is not a converted audio standard like helical scan DAT, or DVD


I agree. In 7 years regular MO usage I have still to see my first
unrecoverable read error. (I had to clean cartridtges two times,
but that resolved the problems with them completely.)

However, the "real" MO systems are based around the 5.25" form-factor:
o New blue-laser ones offer a migration path to very high data capacities
o The 5.25" form factor is relatively well proven in medical/mil/industrial


Actually many hostpitals in Europe use 3.5" MOD for computer images.
They have to keep the info for 20years by law, e.g. in Germany
or Switzerland and a few of these 640MODs are enough for a day.
I would say 3.5" MOD is professional today. 5.25" MOD seems to
have stalled development some time ago.

For the most part, DVD-RAM offers a good half-way house:
o Reliability is good - it is Phase-Change unlike DVD+/-R &
has better error correction
o Drives are cheap - so having 2 different branded drives
isn't impossible (or suppliers :-)
o Disks are cheap - 9.4GB can be had for just 6.99, sealed,
a bit more elsewhere


However there is the cartridge issue. Drop a DVD-RAM and it may
be gone. A MOD does not care. Also remember that MOD has 30 Million
certified overwrites while DVD-RAM without cartridge only has 10.000.
If you only do backups, that does not matter much. I also use my MODs
in "HDD mode", i.e. move around files, do small changes, etc..

MO is ~200 drive & ~10 media for 1.3GB v ~60 drive & ~7 media for 9.4GB.
Critical stuff is best on MO, but with those media errors I think it's
forget about decades:
o Yes, backup media can last a long time - DVD-RAM probably, MO most probably
o However, it is perhaps more economic to keep changing technology every
few yrs
---- because technology will offer more capacity, perhaps more
reliability for less cost
---- that is particularly so with media cost as archives grow - eg,
DVD-RAM v MO


Depends. I have still about the same needs for high-reliability backups.
After I nearly lost some important stuff 7 years ago, I got a 640MB
MO drive. I still get my system and home backups on just two of these
disks and I still have all the original disks and the original drive
in use without problems. The last time I bought disks is 3 years ago,
the ~30 GB ultra-reliable storage I have is more than enough.

For the less critical stuff I keep copies on other computers.

MOD is fit to keep you Master's thesis, family photos, tax data you
need to store for decades (in some countries), scans of your degree,
in short all the things you absolutely do not want to loose. Also most
data recovery companies will convert MOD to some other format for you
for a modest fee and that type of offer should be around really long.
So even if you do not have a drive anymore in 30 years, that data
should still be accessible.

If your storage needs grow fast (my orgiginal complete systems backup
fit on just one 640MB MOD), then MOD is not the right solution
today. (It was by far the cheapest 7 years ago. And it is still
around. That should tell you something.)

Agreed - many people backup to DVD-RAM or HDs "incorrectly"
o They simply drag-n-drop files - directory is there, so it must be ok
o Better to use a proper backup tool - that actually does a proper compare
---- altho even XCOPY can be forced to do a verification as I recall
---- on DVD-RAM that might be an exercise in s-l-o-w-n-e-s-s however


Actually you should script this stuff. I am still surprised that MS
does not deliver a proper and easy to use backup tool with thir OS.
It is not that difficult. I use unix tar, perhaps one of the oldest
UNIX tools with good success.

If HDs are used, I prefer a "micro-PC" converted to NAS - with a few

Yes, that is what I use at home for the less critical stuff.
A Mini-ITX box with a 120GB HDD is just fine for this.

scripts to check the data integrity progressively to another
identical machine working in parallel. That need not be particularly
expensive - Mini-ITX snails don't cost much, recycle some of the
older 1U PSUs, make/re-use a case, whatever. Match solution to data
criticality.


.... and to data amounth and actuallity. Only then will you get
something satisfactory.

Arno
--
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"The more corrupt the state, the more numerous the laws" - Tacitus


  #25  
Old October 15th 04, 02:30 PM
Michael Salem
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nospam wrote:
"Sideshow" wrote:

A raid0 or raid5 array is the most suitable option for long term backup, as
if one drive fizzucks you can just replace it with a new one without any
data loss.


Sure, a small company I know decided a raid array on their server meant
they didn't need to backup. The sever fell over one day and trashed the
whole array, they lost everything. Hard drives inside an active machine are
a very bad idea for long term backup.


Also, FILES get corrupted or otherwise damaged without affecting the
hard disc. It's very nice to have a week's daily backups and a month's
weekly backups on tape (9 tapes).

Best wishes,
--
Michael Salem

  #28  
Old October 15th 04, 05:33 PM
Bernard Peek
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In message , Michael
Salem writes
nospam wrote:
"Sideshow" wrote:

A raid0 or raid5 array is the most suitable option for long term backup, as
if one drive fizzucks you can just replace it with a new one without any
data loss.


Sure, a small company I know decided a raid array on their server meant
they didn't need to backup. The sever fell over one day and trashed the
whole array, they lost everything. Hard drives inside an active machine are
a very bad idea for long term backup.


Also, FILES get corrupted or otherwise damaged without affecting the
hard disc. It's very nice to have a week's daily backups and a month's
weekly backups on tape (9 tapes).


Pretty much essential. In my experience the main use for backup tapes is
to restore files that users have deleted. A RAID array doesn't protect
against that. In fact I haven't ever needed to use a backup tape for any
other purpose, and I've been working with computers for 25 years.



--
Bernard Peek
London, UK. DBA, Manager, Trainer & Author. Will work for money.

  #29  
Old October 15th 04, 05:33 PM
Bernard Peek
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Default

In message , Arno Wagner
writes


Agreed - many people backup to DVD-RAM or HDs "incorrectly"
o They simply drag-n-drop files - directory is there, so it must be ok
o Better to use a proper backup tool - that actually does a proper compare
---- altho even XCOPY can be forced to do a verification as I recall
---- on DVD-RAM that might be an exercise in s-l-o-w-n-e-s-s however


Actually you should script this stuff. I am still surprised that MS
does not deliver a proper and easy to use backup tool with thir OS.


They do. If you understand how to write batch files you can use ntbackup
to do complex scripted backups. It's a very powerful tool but almost
completely undocumented.



--
Bernard Peek
London, UK. DBA, Manager, Trainer & Author. Will work for money.

 




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