How Home Backups Should Be Done(tm) Was: [lug] Tape Drive Recommendation...

[Alan Robertson]

Sean Reifschneider wrote:
> 
> On Mon, Aug 21, 2000 at 08:01:26PM -0600, Alan Robertson wrote:
> >It is important that your full and incrementals all fit comfortably on one
> >tape.  If they don't, then GET A BIGGER TAPE.

Oh Man!  If a post *that* opinionated didn't generate any flames, then what will
;-)
 
> I agree with all your suggestions.  The problem gets back to the idea that
> tape drives just haven't kept up.  One of the next couple of days I'm
> planning on ordering a 60GB hard drive for well under $300.

The Ecrix costs around $400, with tapes being $80 or so each.  Since you need
several (to cover human errors, disaster recovery), the costs are not so far
apart.  To really appreciate tape, you need a jukebox.  To make good use of a
jukebox, you need lots of disk...

> I used to be excited about the idea of using tapes for a kind of
> HSM -- I mean you could get $10 cartridges that held 2 to 4 gigabytes!
> Inconcievable!  Average seek time on a DDS tape drive was around
> 40 seconds -- I could wait 40 seconds for little-used data.  That was
> back when a 1 or 2GB hard drive was over a grand, and a DDS tape drive
> was slightly cheaper.

SCSI drives are a good bit more expensive (and a somewhat more reliable).  HSM
has actually been pretty useless for about 10 years - because tape needs to be
1/10 the price of the corresponding disk to make the changer cost and additional
unreliability (hw/sw) worthwhile.

> Now we've got 10 times the storage for a tenth the price in hard
> drives and, well, still DDS with the drives costing a grand.  The
> capacity has increased by 10x, but the cost hasn't gone down
> a similar amount, which leaves tapes an order of magnitude less
> effective than before.
> 
> So, how about: periodicly spend some time and make a couple of copies
> of a base-line.  A full backup with everything on it.  Then run
> a level 2 backup of things that changed since the base-line and
> append to that additional incrementals.
> 
> I wholely agree that you should only be swapping a single tape every
> week.  Anything more than that and you probably won't do it.

Another thought:  Is this an opportunity in the days of cheaper bandwidth for
people to provide offsite disk storage accessed through the internet?

You make backups for three reasons:

	Protect against media and hardware fubars

	Protect against human fubars

	Protect against site disasters (fires, etc).

For the latter one, tape is still the only real alternative, unless you have a
service bureau which will suck up your bits and store them for a reasonable
cost.  Human fubar recovery requires several copies, spaced up to several months
apart to allow for not finding the mistake until much later.

You can do site disaster recovery with drbd (TCP mirroring), if you can afford
the bandwidth, or make the offsite site reasonably close by.

Maybe electronic vaulting is a new opportunity for tummy.com ;-)

	-- Alan Robertson
	   alanr at suse.com