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Quick BACKUP question

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Art Wiens
Respected Contributor

Quick BACKUP question

I have a tape that has a saveset on it. I want to put an additional saveset on it. ie. not loose the first saveset. If I:

$ BACKUP /NOINIT /NOREWIND ....

this will simply add my saveset to the end of the tape, correct?

Second guessing myself for some reason,
Art
10 REPLIES
Bojan Nemec
Honored Contributor
Solution

Re: Quick BACKUP question

Art,

You can simply mount /foreign the tape and do the backup. Noinit and norewind qualifiers are set by default. If the saveset name is not equal to the tape label dont forget /ignore=label. Backup will append the saveset to the end of tape (The saveset is a regular file).

Bojan
Art Wiens
Respected Contributor

Re: Quick BACKUP question

That's what I thought, but seeing as how the first saveset is "irreplaceable", I really don't want to lose it.

Thanks for confirming,
Art
John Gillings
Honored Contributor

Re: Quick BACKUP question

Art,

>That's what I thought, but seeing as how the first saveset is "irreplaceable", I really don't want to lose it.

Tape is cheap! Don't risk it.

If the data really is irreplaceable your best strategy for not losing it is to have many copies, on different media, widely distributed. Set any copies to disable writing and mark them "do not overwrite".

A crucible of informative mistakes
Uwe Zessin
Honored Contributor

Re: Quick BACKUP question

In the past I have searched for a non-existing save-set to get after the last file on tape (I never felt safe with /NOREWIND ...) like this:

$ BACKUP/LIST tape:nonex.fil

But if the contents are that critical I agree John. I would rather make a copy from this tape than trying to write to it ever again.
.
Jan van den Ende
Honored Contributor

Re: Quick BACKUP question

Art,

I'm really in with John & Uwe on this, and more.

I don't know for HOW LONG this tape is deemed irreplaceable, but as long as that lasts, at least every 3 years do a read-back, and create (a) NEW (set of) tape(s).
Remember: in the old DSA days, BACKUP would reconstruct most 'fallen' bits, it just took some more time and some more CPU to read your tape with (many) recoverable errors.
But now, in the days of SCSI devices, you get ONE parity error, and you are in FATAL DRIVE ERROR, and NO way fo force the drive give BACKUP the remainder of the data to work its magic. (some specialised companies CAN do it for you, but they are JUST A BIT more expensive than some extra tapes!)

So: HAVE multiple copies, and REFRESH them regularly!!!


Success,


Jan
Don't rust yours pelled jacker to fine doll missed aches.
Art Wiens
Respected Contributor

Re: Quick BACKUP question

John - "Tape is cheap! Don't risk it."

Well, yes and no (relatively) SDLT's are ~$150 cdn a throw. Not really "cheap", and it also seems to be a bit of a waste to use a 100/200GB tape to store a 50MB saveset. Risk is also relative, SDLT's are a whole lot more reliable than 8mm's ever were!! ;-) So far (~2 years), I've never had an SDLT tape drive "eat" a tape.

Uwe - "BACKUP/LIST tape:nonex.fil"

Good trick! I'll have to remember that one.

Jan - "So: HAVE multiple copies, and REFRESH them regularly!!!"

As always, good advice...I wonder how many shops actually do this type of rotation?

Thanks,
Art
Jan van den Ende
Honored Contributor

Re: Quick BACKUP question

Art,


So far (~2 years), I've never had an SDLT tape drive "eat" a tape.


Who says coincidences don't happen?

We got one just yesterday....
Luckily, "only" a daily backup tape, so the loss is only the cost of one tape, and the extra risk of having a one day older backup (which reset itself the next night)


As always, good advice...I wonder how many shops actually do this type of rotation?


Many of our tapes are required by privacy laws to be destroyed after 3 years, so that's easy.
Others we are required to retain until released by court processes reaching finality. THOSE get cycled!


Interestingly, we DO have something like your procedure in operation as well.
Data entry traces of some (3 different) sensitive apps need to be retained, and are taped regularly.
Weekly they are appended to tape, cycled each year.
The sheer volume of 3 sets of new tapes each week is prohibitive.

So, we make multiple sets.
Sometimes a tape fails, and we found if we then declare it read-only, all but the last saveset are readable.
So we redo the last saveset on a new tape, and we end up overall with about 10 % of the collections destined to be on one tape to be spread over two.
So, weekly saveset, avarage 2,2 tapes/year.
Both in raw tape cost, and in vault space, still a lot cheaper than 52 tapes!


Jan
Don't rust yours pelled jacker to fine doll missed aches.
Ian Miller.
Honored Contributor

Re: Quick BACKUP question

The cost of a SDLT tape is trivial compared to the worth of the data. The people cost tend to rapidly become alot more than tape costs. However it's sometimes difficult to get people to understand this.
____________________
Purely Personal Opinion
Bojan Nemec
Honored Contributor

Re: Quick BACKUP question

Art,

I agree with all others. Do not risk with tapes. Appending save sets can be used for daily backups, where you dont lost data, only a litle extra risk, as mentioned by Jan. For "irreplaceable" data use new tapes and write protect them.

And to skip to end of the tape you can use:
$ SET MAGTAPE/SKIP=END_OF_TAPE

Bojan
Alvescot
Advisor

Re: Quick BACKUP question

If you have the temporary disk space and time, you could always do the following:

Mount/over=id mka100:
copy mka100:saveset.bck dka100:

Then dismount the tape and do your backup of your new saveset. Then to check everything, remount the tape as above and do a directory listing on the tape. You should then see both your savesets or however many savesets you have on the tape.