Re: [gentoo-user] {OT} offline backups

[Rich Freeman]

On Fri, Mar 6, 2015 at 1:15 PM, Volker Armin Hemmann
<volkerarmin@××××××××××.com> wrote:
> Am 06.03.2015 um 18:10 schrieb Grant:
>>>>> On Tue, Mar 03, 2015 at 07:51:35AM -0800, Grant wrote
>>>>>> I have several encrypted backup repositories online and I'd like to
>>>>>> somehow mirror that offline.  I currently have about 20G of data to
>>>>>> back up.  Any ideas?  Rewritable Blu-Ray?
>>> It would seem that this is a backup to a backup.  I think I read earlier
>>> that the OP already has backups but just wants more backups just in
>>> case.  I guess one can never really have to much, I guess.
>>
>> The idea is to have an offline backup in case all of my online stuff
>> is infiltrated.  Should I just connect a USB tape drive, USB hard
>> drive, or USB flash drive when I want to back up the backups?  Can
>> tape be rewritten?  If not, that may be the best choice so I can leave
>> it connected all the time and not worry about it being deleted.
>>
> 'connected all the time'? You seem not to know how tape works?
>

To be more explicit:  Typically the workflow with tape is to rotate
your media storing each backup on a new tape, with not-in-use tapes
stored someplace safe (often a fire safe for short-term storage, and
off-site for long-term storage - depending on level of paranoia and
willingness to deal with expenses).

I need to look on EBay some time but tape isn't nearly as cheap as
some seem to be making it out to be.  Hard drives have sized up so
quickly that it is no longer common to be able to buy a cheap tape
drive that can store a few hard drives on a single tape.  An LTO-6
tape stores 2.5TB (uncompressed) and costs about $35.  A drive capable
of writing on it costs about $2k new.

Tape makes sense for its longevity, but cost-wise it only makes sense
if you're writing a LOT of tapes.  If you needed to store 10 tapes
worth, hard drives would still be cheaper.  If you had to store 20
tapes worth, the tapes would probably be cheaper.  Obviously if you
can get a great used deal on the tape drive and it is in good shape,
then the economics change.

So, when you're storing on tape it usually makes sense to rotate your
media and not keep overwriting/appending the same tape over and over.
After all, you made the big expense for the drive already, and the
tapes are relatively cheap (though not trivially so).  Hard drives are
a different story, and since hard drives are less durable in general
it might make sense to avoid moving them around more than you have to.

If you really only have 20GB of data and it is really important, it
looks like you can pick up LTO-1 drives for $20 and tapes for about
the the same kind of cost.  Granted, USB sticks are still going to be
cheaper, but the reliability of tape is very good (reliability of $20
used drives, probably not so much but if it fails on a restore you can
probably always buy another $20 drive as long as you can get your tape
out of the thing).

I think a lot of places have been moving more towards hard drives for
backup though, unless it is for archival (write once, save for 10
years).  If I want to save 1000TB to hard disk, I can buy 300x3TB
drives and write my backups at a rate of 300xSATA speeds.  If I want
to save 1000TB to tape I need 300 tapes (much cheaper), and then
either 1 drive stuck writing at 160MB/s (which is way cheaper than the
hard drives), or have many drives which scales up the writing speed
but ultimately becomes more expensive than the hard drives.  The
advantage of the tapes comes if you want to hang onto full backups for
a long time.  There is a reason companies like backblaze are using
hard drives.

I wish tape was a practical option for me, but my backups currently
consume 3.7TB.  I'd much rather have offline tapes instead of a pair
of online hard drives storing only a few days worth of de-duped
backups (using rsnapshot).  However, the pair of drives costs only
$200, and storing that kind of volume using tape right now would cost
me $2100, with the need to swap tapes every time I did a backup (vs
automated nightly backups currently).  The tapes would of course be
far more secure if some malware came along and decided to wipe things,
and a small subset of my data is backed up to the cloud to mitigate
against this and other localized disasters.

-- 
Rich