Re: REPOST: RMAN question

From: Howard J. Rogers <hjr_at_dizwell.com>
Date: Wed, 01 Sep 2004 13:13:22 +1000
Message-ID: <41353e6e$0$5450$afc38c87@news.optusnet.com.au>

Daniel Morgan wrote:

>>>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.

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.

[snip]

> 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.

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

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

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 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.

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).

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"

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. 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.

> 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! 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

-- 
http://www.nicecupofteaandasitdown.com

Received on Tue Aug 31 2004 - 22:13:22 CDT