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number of read/write passes

 
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New Member

number of read/write passes

This web site show the dlttape iv is good for 1million read/write passes. I have printed a media set log from backup exec and it shows total write mb - is this the same thing as read/write passes?
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Trusted Contributor

Re: number of read/write passes

No those are different values.

Read/write passes is a measure how often the tape medium can be passed over the head before it wears out.

The total mb value reported by your software is the amount of data written to your tape by the software, which is a different measure.

Some software also keeps track of number of overwrites, showing how many times the tape has been written to from the beginning. However, since this does not count read operations, and number of times a tape was loaded until it was full (appended to), it does not translate to the total number of times the tape passed over the head.

In addition to this, if you drive does not stream (doesn't get the data fast enough from the host) it does what is sometimes referred to as shoe-shining (stopping, repositioning, restarting) which causes a lot of movement of the same porition over the head.

In general there is no way to find out how many times the tape passed over the head, and the value would differ for different portions of the tape in the same cartridge.

I wouldn't worry about this though, as 1 million passes is a lot of tape movement, and I have yet to see a cartridge that failed for exceeding this specification. It will fail for many different reasons long before than.
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New Member

Re: number of read/write passes

Thanks for the info. I'm not so concerned about the tapes 'failing' as much as the writes failing. You know, data integrity. Is there any chance the tape will not write accurately after a certain number of uses, hours, mounts, writes? You know what I mean? I know it's not likely the tape itself will fail, some of the tapes are stored for as long as a year, will the data be as 'fresh' then as when written if the tape has already been used over and over hundreds of times previously?
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Honored Contributor

Re: number of read/write passes


Try this document:

http://www.hp.com/cposupport/information_storage/support_doc/lpg50069.html



John
Eagles may soar in the clouds but weasels don't get sucked into jet engines
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Occasional Contributor

Re: number of read/write passes

 

Hi, the link is broken, did you have a new  reference?

 

I'm interested on this topic since I'm worried about know how long should I replace the tapes.

I'm using DAT 160 cartridges from HP, which have an MTBF of 2000 passes or 100 backups, but how can I know this number on every tape? Can't find any option on DPE 3.5 SP2

 

Or do you know if the DPE alerts me when is time to change the tape?

I had have alerts from the cleaning tape since the unit rejects to use it after several passes...but don't know what happens with media tapes.