topic Re: Tape usage in Operating System - HP-UX

Tape usage

CHRIS_ANORUO — Wed, 18 Dec 2002 09:11:36 GMT

Hello All,

I have lost touch and would like to know how many times I can reuse a DLT tape or DDS3 and DDS4 tapes. Also, where is the backup config file located on the HP 9000 server.

Regards

Chris

Re: Tape usage

Stefan Farrelly — Wed, 18 Dec 2002 09:15:43 GMT

You can reuse them as many times as you wish. There is a software reuse count with high level backups like Omniback, you can reset it in there, or for fbackup it depends on where the -c (config file) option on the fbackup command points to - normally /var/adm/fbackupfiles/config
and it has an option in it called; maxvoluses (which you can simply increase)

Re: Tape usage

Robert Thorneycroft — Wed, 18 Dec 2002 09:30:23 GMT

DLTs are good for 1,000,000 head passes, although you should remember you get multiple head passes on a single backup, especially if the tape drive needs cleaning.

We tend to run our DLTs for 100 backups before we replace with new media as experience showed that using them much more resulted in backup/restore failures which is the last thing you want!

Kind regards,

Robert Thorneycroft

Re: Tape usage

Robert Thorneycroft — Wed, 18 Dec 2002 09:36:27 GMT

It also looks like your DDS tapes are good for 15,000 loads / unloads from a cartridge durability point of view, although whether the tape is good for this many backups is another matter, (Sorry could not find any data on that!) I would suspect the number of backups again would be far lower than this value.

Kind regards,

Robert Thorneycroft

Re: Tape usage

Dave Wherry — Thu, 19 Dec 2002 14:58:27 GMT

I've seen this behavior with DDS tapes and fbackup. There is a counter and once the tape has been used 100 times fbackup will reject it. You can get around this by simply writing something to that tape using tar. That will overwrite any header information on the tape and the next time fbackup uses it, it appears like a new or at least different tape.
I know this because I had a remote office where one of the accountants was supposed to change the tape for me each night. Like clockwork, every 101 days I would get an error on the backup that the tape had been used 100 times. I would reinitialize it and the backup would run fine. Of course this meant the other tapes I had sent him were very low mileage.

Re: Tape usage

Steven E. Protter — Thu, 19 Dec 2002 15:26:57 GMT

We've never had a DLT tape(Ultrium is our standard) die that we didn't drop on a concrete surface(which is below the raised floor, good story there).

Another good thing about Ultrium drives is you needen't clean them unless they indicate they need to be cleaned. That hasn't happened yet either and we've had a large HP unit for over a year.

Its good practice to get tapes out of the media pool after a certain number of uses, as noted above. What I do with such tapes is put stuff on them people want to keep longer term.

A database or system snapshot that we can live without, but might be nice to have should we need to look at 10 year old data. In our business strange projects like that do come along.

Since background radiation can effect data on tapes(so says the experts, never happened to me), really important snapshots go to CD which has a longer shelf life.

Steve

Re: Tape usage

Rory R Hammond — Thu, 19 Dec 2002 21:40:44 GMT

DDS tape have a end of life.

I would not write to them more than 100 times I have had recovery failures on old tapes.

HP dds media guide does have specifications that you can search for on the web.

The following link: has some good dicussions:
http://www.datman.com/tbul/dmtb_035.htm

You DO need to keep track of usage or risk a nasty surprise.

Rory