[Pc_Support] Re: Tape drive for small file server .... -- LTO (unless you have existing AIT or DLT assets)

[Bryan J. Smith]

On Sat, 2006-06-17 at 22:43 -0400, Carter Manucy wrote:
> Just a couple of nit-picks here:
>   ...  
> LTO is only 1-generation fully (read/write) backward-compatible,

Yes, I was aware of this, but thanx for pointing it out.
LTO-2 drives can write LTO-1, but LTO-3 can't.

> and 2 generations read-only compatible...

Huh?  Now that's news to me.  I guess it's hard to say anything for sure
at this point, because only LTO-3 is out and it reads back to LTO-1.

Now I've been following LTO since near inception, but maybe they have
changed their standards/promises as a result of product developments.  I
guess I should read the LTO site since it's been awhile.

> eg, you can read/write to an LTO-2 
> or LTO-3 tape in an LTO-3 drive, but not only read an LTO-1.  LTO-4 
> wouldn't be able to read LTO-1.
> From http://www.lto.org/newsite/html/about_faqs.html
> *Q12: What are the backward compatibility characteristics of the Ultrium 
> format?*
> A12: The LTO Ultrium compatibility is defined with two concepts 
> demonstrating investment protection:
> 1) An Ultrium drive is expected to read data from a cartridge in its own 
> generation and at least the two prior generations.

Interesting.  Okay, I guess that's changed since the original standard. 
Thanx for that update!  Again, I guess I should have read the LTO site
since it's been awhile -- I'm basing my statements on the original
standard/promises plan.

The original LTO standard was to be 4 generations -- with any newer
generation being able to read any older, but only write 1 generation
back.  Again, actual developments have changed the standards/promises,
especially with LTO-4 in development.

> 2) An Ultrium drive is expected to write data to a cartridge in its own 
> generation and to a cartridge from the immediate prior generation in the 
> prior generation format.
> Also, you'd mentioned:
> There is actually a planned Gen 5 and Gen 6 now (1.6TB/360MBps and 
> 3.2TB/540MBps, respectively)

Okay, now this makes more sense.  I assume:  

1.  They've run into some issues reading LTO-1 with the LTO-4
prototypes, and

2.  They've decided with the success and vendor support of LTO to
continue with a 5th and 6th generation, hence

3.  The new clarification on how many generations back can be read.

Hmmm, from a longevity standpoint, this is a bit disturbing.  If they've
clarified this because they are, indeed, having issues with LTO-4
reading LTO-1 -- and there are 5th and 6th generations, then it makes
you wonder if you should start with LTO-1.

I had always recommended LTO-1 because I had believed (from the original
design) that it would be always readable by the terminal generation
(e.g., LTO-4) as in the original plan.  I guess this is no longer the
case so I have to re-evaluate that recommendation.

Thanx for the update Carter!  In any case, I need to blog this.


-- 
Bryan J. Smith           Professional, technical annoyance
mailto:b.j.smith at ieee.org     http://thebs413.blogspot.com
----------------------------------------------------------
The existence of Linux has far more to do with the breakup
of AT&T's monopoly than anything Microsoft has ever done.