Re: REPOST: RMAN question

From: Daniel Morgan <damorgan_at_x.washington.edu>
Date: Tue, 31 Aug 2004 19:38:26 -0700
Message-ID: <1094006364.246744@yasure>

>>I too have formatted a lot of hard disks. But never one with static
>>content put away for safe storage.

>
>
> I can remember us putting a hard disk away once. Not for archiving purposes,
> but with the intent of sometime sending it away for a bit of data recovery.
> I caught a junior fetching it out from the filing cabinet one evening,
> intending to install it into a user's workstation since their own hard disk
> had failed...

I guess you do things differently down under than we do them here in the colonies.

Here when we use hard disks for back up we put them in boxes and ship them out of state to places designated as safe data respositories.

What you describe could have, as easily, happened with a tape. And I don't think supports your conclusion that tape storage is safer than hard disk storage when used for backup and recovery.

>>Now the question that really matters. What makes you confident that
>>those tapes you sent off were usable for recovery 5+ years later? 10+
>>year later? Or more?

>
>
> I doubt the tape drive we recorded them on would still be usable today.
> That's why we transferred stuff which really did have to be kept
> "forever" (and not just for many months) onto CD (as it then was) and DVD
> (as I would probably do today).
>
> This isn't rocket science. People have had to discuss the issue of long-term
> storage of critical data many times over the years (and let's leave aside
> the fact that I doubt a program exists these days that could read the data
> I considered critical back in 1987). If you want storage that will last for
> millenia, get out your chisel and hammer. Short of that...
>
> Of all the possibilities for long-term (ie, many, many months) storage, I
> don't think I've ever heard a hard disk seriously suggested.

You have from me. ;-) And I know it is used as the "best practice" at a number of large firms.

  That could
> just be me, of course. Or it could have something to do with the fact that
> there is no write-protect tab for a hard disk (see note above).

And also note that a file cabinet is not an off-site data storage repository.

  That one
> drop on the server room floor toasts the disk. That an airline of my
> acquaintance is very iffy about transporting hard disks it can't plug in
> (and potentially destroy in the process), but is not so concerned about a
> DVD or CD-ROM. And so on. Hard disks are big and bulky. CDs are not. Tapes
> are fairly robust; hard disks are not.

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

> I can think of no medium which screams out "I am short term" more than a
> hard disk. Nor one which better cries "I am a reasonable medium-to-long
> term proposition" than a tape.

I felt the same way but then I got my start back in 1969 when storage media meant tape. I don't think that is true any longer.

> And I know you won't believe me, so try believing an institution such as the
> British Museum whose very existence is predicated, to some extent, on
> making these sorts of decision. To which end you might read
>
> http://www.ukoln.ac.uk/services/papers/bl/jisc-npo50/bennet.html
>
> And in particular, section 5. The opening sentence of which reads
>
> "In the last 50 years, the diversity of media on which data has been stored
> has not diminished, but increased. Despite the diversity, the most durable
> of media remains the tape."

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.

> As they go on to conclude: "...it is the opinion of the team that there is
> no real choice over the ideal media for long term preservation of digital
> material. The media that should be used is either 8mm DAT volumes or some
> derivative of CD ( a new CD format may require bulk copying of data)."
>
> Despite their lack of hard conclusions, you might note that the hard disk
> did not feature in their final choices.

But did they run a real test or just make assumptions?

> Now you might conclude that the paper dates from 1997 and is therefore
> worthless (and I'd agree with you regarding their conclusion that Windows
> 95 and SCO Unix were safe long-term bets!). But I could post you other
> papers from similar institutions of more recent vintage that come to much
> the same conclusions.
>
> Regards
> HJR
Well based on their confidence in Win95 and SCO one couldn't one draw a reasonable conclusion about the decision makers eh?

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

Received on Tue Aug 31 2004 - 21:38:26 CDT