Suggested method for predicting need for tape changes

[philx509]

I use Retro for Win 6.0 Professional, and I am mildly frustrated by the lack of convenient tools to predict a tape change. here is a suggestion:

 

Take the average of the past N days (user selectable) size backup. Assumption: today's backup will be close in size to that average. Compare with the space already used on the tape.

 

Also, keep track of the actual capacity of each tape (by size, if necessary) for that backup set. You should be able to do this easily because Retro knows when a tape change is necessary.

 

Keep this statistic for all backup sets. Allow the use to select which backup sets will be part of this calculation.

 

This method would determine for that user's application, the actual capacity per tape, and the average day's backup. Using this data, it should be relatively easy to estimate when a backup job will not fit on the current media. That would allow the operator to use a new tape, or be prepared for a tape change in the middle of the backup job.

 

In Northern California PG&E (utility company, for non-Californians) uses this approach to smooth out the customer's monthly bills.

[natew]

Hi

 

I see your point but its just not that easy. There are many factors that affect tape capacity - the amount of data being backed up is only one of them. Even with past backups as a reference point judging tape capacity is a shot in the dark.

 

If your nervous about when a tape will get full your best bet is to set the "automatically skip to blank media option" and put a blank tape in the drive for that nights backup.

 

Thanks

Nate

[philx509]

Quote:

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Hi

 

I see your point but its just not that easy. There are many factors that affect tape capacity - the amount of data being backed up is only one of them. Even with past backups as a reference point judging tape capacity is a shot in the dark.

 

 

 

Thanks

Nate

 

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Nate. I do understand that in general it is hard to predict effective tape capacity because of uncertainty about data compression ratios. However, by looking at the history _for the same kind of data_ you would have a "reasonable" indication of compression ratios.

 

Is it too much to ask that someone in engineering or product management consider this issue, and maybe visit some customers and look at their actual backup experience, that is, the effective tape capacity for a given kind of data.

[natew]

Hi

 

Quote:

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Is it too much to ask that someone in engineering or product management consider this issue, and maybe visit some customers and look at their actual backup experience, that is, the effective tape capacity for a given kind of data?

 

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Of course not. User feedback is what this forum is for.

 

My intent was to give you a better idea of the issues involved and why the product works the way it does. It was not intended as a rejection/refusal of your feature request.

 

Thanks

Nate