Backup and recovery

[AC]

On 2015-12-19 05:59, Jean-David Beyer wrote:
> On 12/19/2015 08:37 AM, Mike or Penny Novack wrote:
>> On 12/18/2015 9:16 PM, Jean-David Beyer wrote:
> 
>>>
>>> I do a full backup of almost my entire system every night to an external
>>> USB-3 hard drive. I do a full backup of almost my entire system every
>>> week onto magnetic tape that I keep in another room from where my
>>> computer is. I do a full backup of almost my entire system every week
>>> onto magnetic tape that I keep in my safe deposit box at my bank.
> 
>> THIS is an example of doing backup (although using obsolescent
>> technology, since a modern external hard drive the size of one computer
>> tape cartridge holds FAR more data and could rotate one to the other
>> room, bank vault, etc. ---- I keep a second copy in a fire box inside a
>> dead fridge in an outbuilding.).
> 
> You are right that magnetic tape technology is obsolete, although the
> tapes I use are VXA tapes originally produced by Ecrix. They are
> extremely reliable, and I can fit many months of these tapes in my safe
> deposit box, whereas I can put only a very few WD-Passport drives in
> there. I like to keep a year's worth there (12 cassettes take up much
> less space than 12 Passports). OTOH, when these tape drives quit, that
> is over as no one makes tape drives like these anymore. That is why I am
> using the Passports for the shorter term (daily) backups.
>>
>> You have LOTS of user data on your computer system besides gnucash data.
>> Rather silly to have each application responsible for backing up the
>> data with which it is associated.
> 
> Absolutely! By Murphy's law, each application would use a different
> backup strategy, different storage formula, etc., so that restoring
> would be completely unmanageable.
> 
>> You wouldn't expect your word
>> processor to be doing the backups for the documents it created, would you?
>>
>> The backups made by gnucash are really intended for use with problems a
>> short time back (since the last full data backup). If you are not doing
>> regular backups then sooner or later you will lose your data. It's not
>> if computers fail but when. If you do not have a "tech support" to do
>> your data backups and restores then you have to learn how to do it
>> yourself. Part of successfully using a computer.


Tape is not obsolete.  LTO (Linear Tape Open) is the current standard.
A single LTO-6 tape which is nominally the size of a USB external hard
drive case that fits a standard 3.5-inch hard drive (not a laptop sized
2.5-inch drive) can hold 2.5 TB uncompressed.  LTO-7 due out in late
2016 is the same size tape with a 6.0 TB uncompressed capacity.  Nominal
compression is 2.5:1 so the LTO-6 2.5 TB becomes 6.25 TB and the
upcoming LTO-7 will be about 15 TB.

The advantage of tape is that more media can be physically added to a
tape design (possibly making the cartridge slightly larger) without
changing the underlying technology.  Hard drive read/write head
technology coupled with the magnetic coating technology requires
significant leaps to achieve higher write densities in what is a very
restricted form factor (the drive can't change shape or it won't fit
into the machines).  The tape technology can be updated as well (better
materials, better hardware) to increase data density but storage size
doesn't stay coupled to technology advancement.