Re: REPOST: RMAN question

From: Daniel Morgan <damorgan_at_x.washington.edu>
Date: Wed, 01 Sep 2004 22:22:04 -0700
Message-ID: <1094102583.338898@yasure>

Howard J. Rogers wrote:

>>What you describe could have, as easily, happened with a tape. 

>
>
> Of course it could. But how many times have you ever wanted to install a
> spare tape into a user's PC because their tape had failed? So whilst it
> could have happened to a tape, it is vanishingly unlikely that the
> motivation ever to do it would arise in the first place.

Never. But then if the tape had been properly stored at an off-site repsitory the issue wouldn't have come up. Same goes for a hard disk. And when it comes to backing up Oracle servers I try to keep those important backup items in the server room not in file cabinets.

Perhaps just another one of those American quirks. ;-)

>>True. But hard disks are blazingly fast compared with tape and no more
>>expensive per GB.

>
> Likewise true. But I thought we were talking about archiving and long-term
> data storage? Not speed of taking a backup.

We were. And I guess if the point is to have storage that will last for 50 years I couldn't hazard a guess as to which would be of value given that the operating system and hardware used to create it would no longer exist. But for any reasonable period I think hard disks are of equal or lesser price, just as likely to survive in proper storage and a heck of a lot faster.

> If you want speed, disks are good. Of course. They are always my first
> backup device whenever possible, precisely for that reason.

A point of agreement.

> But if you want robust, long-term storage, then you forget the speed issue
> and concentrate on robustness... which you've just agreed disks lack in
> comparison to tape or other storage media.

I don't recall agreeing on that. I recall saying I don't think either of us has ever had reason to pick up a 5 or 10 year old tape and find out. And I thought you'd agreed with that.

>>I know a lot of people think that. And compared with diskettes, CDs and
>>DVDs I'd agree. But I don't think the needs of an IT department are
>>truly one of needing to restore to five years ago even though I tossed
>>you that red herring. I think for the period of time when a backup might
>>reasonably be used (1 day to 1 year) hard disks are as safe, if not
>>safer, definitely faster, and in my opinion less expensive.

>
> Then we are talking about different matters, and not -incidentally- about
> what the original poster asked, nor the point I was addressing when I
> replied to him (and which I thought you were discussing).

Probably true. I never get to these posts until close to midnight and after a bit of velvet smooth single malt scotch.

> To remind you. The OP wrote: "I need to retain a few backupsets forever".
> And I wrote "[backups are] a lot more safe on tape 'forever' than they would
> be on disk"

Ok "forever" but with the hardware in the dumpster years before. The operating system long since forgotten. Even if the tape survived ... so what? And I am still not convinced the hard disk wouldn't survive just as long.

Someone saying "forever" is like someone saying "real time". If real time means instantaneously they are going to have to wait for quantum computing or the repeal of the laws of special relativity.

> Now, you can re-define "forever" to mean "1 day to 1 year" if you wish, but
> I'll decline that opportunity, if it's OK.

Ok with me. Going back to my Cobol days and thinking about the year 2000 I considered forever to be about 20 years and so did all of my contemporaries. ;-)

My personal experience has been,
> several times, a requirement to produce an archive that will survive for a
> minimum of seven years (thanks to the tax and corporation laws here).
> That's the sort of thing I think our OP was talking about, and what I was
> addressing, too.

Seven years in the U.S. for tax purposes too. And I've yet to find a 7 year old hard disk that failed sitting in secure storage: Perhaps others have.

>>Well based on their confidence in Win95 and SCO one couldn't one draw a
>>reasonable conclusion about the decision makers eh?

>
> You can sometimes be predictable! I knew you would want to seize on that
> detail, so I mentioned it explicitly to try and head you off at the pass!

I try to never pass up a chance for humor.

> Ultimately, it makes no difference: we're discussing the long-term
> viability of the storage media themselves, not the technology needed to
> read those media. The O/S being used at the time is not a significant
> modifier of the conclusions regarding the robustness of a particular
> physical media format.
>
> These guys work for the British Museum. They do long-term storage (for
> centuries) for a living. I think the results of their deliberations have
> merit.
>
> Regards
> HJR
I agree with your assumptions about those folks at the museum. But I question whether anyone has actually run tests that bear this out as factual rather than anecdotal.

-- 
Daniel A. Morgan
University of Washington
damorgan_at_x.washington.edu
(replace 'x' with 'u' to respond)

Received on Thu Sep 02 2004 - 00:22:04 CDT