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Neebie ?-Tape capacity- how full?


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How do I determine if a tape is full or how much storage space it has left??

I have a Xserve (intel) OS 10.4.x, and a Xabyte 2u VXA drive with 10 tape capacity. I need to figure out when I need to replace full tapes and store the full ones. I've looked into retrospect help, and the program to find out the remaining storage capacity and found nothing. Am I missing something??

Thanks.

Ken W computergrem1.gif

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How do I determine if a tape is full...

 


Go to Configure. Backup Sets> Configure[name of backup set]. The Summary tab will list the number of tape members in the backup set. If the latest tape member still shows some capacity (no matter how small), it's not full. All previous tape members of the backup set are either full (most likely) or have been flagged as missing.

 

The Members tab in the same window will list the actual amount of data on each tape member, when the tape was first written to, and whether you have flagged it as missing (the listing will be preceded by a "poof" symbol instead of a checkmark).

 

Quote:

... or how much storage space it has left??

 


Due to various factors such as compressibility of files, network transfer speeds, etc., the actual capacity of a given tape will differ under different circumstances, sometimes by a factor of 50% or more, so the remaining capacity displayed by Retrospect is only a guess (and may be wildly wrong for that tape). Viewing how much data was actually written to each of your previous tape members over time, as described above, will at least give you some clue as to the ranges you may be able to expect in your particular situation.

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Well, actually you are, in a sense, asking an unanswerable question. The amount of data storage space left on a tape depends on the length of the tape (its nominal capacity), whether or not you have compression enabled, how compressible your data is, and the specifics of how efficiently you are able to pump data to the tape (whether it is "backhitching" or whether you have the drive in a mode to adjust write speed to match available data). You can use the exabyte tool to adjust the settings on your drive. Retrospect will write until it sees EOT.

 

Didn't know that Exabyte made a 2u VXA drive with 10 tape capacity - our Exabyte VXA-2 with 10 slot autoloader is 1u.

 

Be aware also that there is a bug in Retrospect's handling of barcoded tapes, if you are using barcoded tape inventory, that prevents management of barcoded inventory. The bug is, even if you have pre-named, pre-erased your tapes so that the correctly named barcoded tape exists in the autoloader the next time Retrospect needs to move to a new tape, Retrospect will ignore the names of the erased tapes and whimsically chose one of the erased tapes in the autoloader for writing. I turned in a bug report on this under our service contract a couple of years ago, but it has never been addressed. It was fixed in the Windows version years ago, but never has been fixed in the Macintosh version. I've waved the flag for years to get this fixed, but I've given up because Retrospect doesn't appear to be being maintained any more. Big help our support contract was on this, because it's been ignored.

 

This bug has a dangerous interaction with Retrospect's algorithm to decide whether a tape is "erased", in that Retrospect decides that a tape is erased if it is unreadable at BOT. Point being, if your tape drive needs cleaning, or if your tape drive can't read a tape for some reason on insertion, it will decide that the tape is "erased" and might declare it eligible for scribbling the next time an erased tape is needed.

 

Now, to your question, as best it can be answered:

 

Go to "Configure > Backup Sets", select a backup set, click "Configure". Under Summary, "Available", if it says "appending requires another member", then all of the member tapes in the backup set are full. If you click the "Members", button, you will see the amount of data on each tape member.

 

Check your "Preferences", "Media Request", "Automatically skip to new media" setting in view of the above.

 

Regards,

 

Russ

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Hi all,

 

i would like to find out what it is that determines the capacity of tapes.

 

My backup runs on two sets of 10 members and on average I get 80 GB on each tape (LTO-1), the volume varying from a minimum of 62GB to a maximum of 109GB.

Tapes with the same ordinal in each set hold more or less a comparable amount of data respectively.

What is it that influences this wide discrepancy between tapes' capacity?

 

many thanks

 

LC

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Quote:

i would like to find out what it is that determines the capacity of tapes.

....

 

 


Did you take the time to read my post above? I answered that question:

 

Quote:

Well, actually you are, in a sense, asking an unanswerable question. The amount of data storage space left on a tape depends on the length of the tape (its nominal capacity), whether or not you have compression enabled, how compressible your data is, and the specifics of how efficiently you are able to pump data to the tape (whether it is "backhitching" or whether you have the drive in a mode to adjust write speed to match available data). You can use the exabyte tool to adjust the settings on your drive. Retrospect will write until it sees EOT.

 


There is also a FAQ on this very subject in the Retrospect Knowledge Base. Next time, you might try searching there first for your answers, but here is a link to that FAQ article:

Tape Capacity FAQ

 

Russ

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