[ale] archiving backups

[Alex Carver]

On 2014-08-06 12:55, Paul Cartwright wrote:
> On 08/06/2014 03:46 PM, Alex Carver wrote:
>> Neither.  The nominal retention time for NAND flash is 5 years or less,
>> depending on the number of cycles of reads and writes to the cells.  The
>> charge stored in the gate oxide bleeds away after some time leading to
>> the memory cell losing that bit of information.  This is especially
>> important for the larger capacity flash devices which use MLCs to
>> achieve the larger capacity.  That retention time is also factoring in
>> the abilities of the on-board ECC to correct for lost bits.  For long
>> term storage go with properly stored magnetic media.
> magnetic media?? for home use? like what. Just askin:)
> I have about 70GB of photos that I have right now on a number of USB
> sticks.. the 64GB stick took 24 hours to complete the copy command..
> oops, sorry, just checked, now it is 92GB of photos..
> 

Yep, magnetic media :)

Since the whole thread was focusing on long term storage with some of
the stored data being decades old I opted to point out the problem with
the goal versus the media.  If this data is to continue to reside in
some long term storage then flash is right out because of its retention.

The other topic point was the value of the data to the end user.  The
thread overall makes a suggestion that the data is irreplaceable and
therefore quite valuable to the end user so I went with that, too.

Option one is a spinning hard drive.  Plug it in, back up the data,
power down and store in a cool, dry place.  If the long term storage
backups are very infrequent, the drive will last many decades and the
data retention is high for the platter media in proper storage
environments (20-25 C, 40-60% RH non-condensing or dry nitrogen if you
go all out).

Option two is tape. You can use the DAT format like DAT-160 which stores
80GB uncompressed per tape (and may be cheaper than the more recent
DAT-320 -- 160 GB per tape.)  HP currently sells a DAT 160 drive for
$700+ while DAT 160 tapes are about $40 each.

DLT is another option for tape media.  SDLT I is 110 GB per tape, SDLT
II is 300 GB, or go so far as DLT S4 which is 800 GB per tape.  There's
a drive on Amazon for about $500.

LTO is yet a third option with some giant capacities in the later
versions.  LTO-1 is 100 GB uncompressed and the current LTO-6 is 2.5 TB
(not GB, but TB).  LTO would be one of the most current though an older
LTO-1 or LTO-2 drive could be purchased.