Capacity less on 1 of 3 Disk Media Sets created same way

[DavidHertzberg]

I have 3 identical 512GB G-Tech G-Drive Slim drives: "G-Drive Red", "G-Drive White", and "G-Drive Blue" (I'm a patriotic American, even if the drives are made in China from a Japanese design ;-) ). On each drive I have a correspondingly-named Disk Media Set: "Media Set Red", "Media Set White", and "Media Set Blue". So far as I can recall, I created each of the Media Sets the same way, although not at the same time ("Media Set White" was a File Media Set for the first week I used it--I changed it when I recycled on the advice of A. of Retrospect TS, and I bought "G-Drive Red" at the same store two weeks later when I realized two media sets were insufficient for weekly rotation when the off-site site is a bank safe-deposit box).


Retrospect 12 shows that "Media Set Red" and "Media Set White" have Capacities of 465GB, but "Media Set Blue" has a Capacity of 292GB. Neither a couple of rotational Recycle Media Set backups nor a Rebuild of "Media Set Blue" has changed that Capacity figure.


Get Info shows the same size of 512GB for all 3 drives, which all have a GUID partition scheme. What could I have done that would make "Media Set Blue" different? How can I expand its official Capacity (just before I Recycle it in two weeks)?


BTW, I also found a definite bug in the course of doing the Rebuild of "Media Set Blue". The Console showed no Active script after the Rebuild portion of the script was finished, but the log said a Verify had been canceled due to user intervention after one minute. I then did a separate Verify, which never showed up as an Active script even though the log said a Verify operation had completed successfully after 38 minutes.

[twickland]

If you go to the Members tab for Media Set Blue and click on the edit pencil, what information does Retrospect display regarding the allowed percentage and capacity of the destination volume? If less than 100%, you can change that figure. 

 

While you're at it, note whether the total allowed capacity differs from the Space Total displayed for that media member, and/or for the media set as a whole (assuming that the set has only one member)? We have found that the total capacity for a media set member that's displayed in the console can be obviously incorrect, as in the screenshot below for a 4 TB member. We've also observed that the allowed capacity displayed in the edit window can differ from the displayed total capacity for a single-member media set. I'm not sure what all this means, but the variation does not inspire confidence.

 

[DavidHertzberg]

If you go to the Members tab for Media Set Blue and click on the edit pencil, what information does Retrospect display regarding the allowed percentage and capacity of the destination volume? If less than 100%, you can change that figure.

 

....

 

Thanks, changing that to 100% fixed the problem.

 

BTW, I also tried changing the allowed capacity to 500GB, but it snapped right back to 465GB. Any idea why Retrospect sets the allowed capacity to a figure significantly lower than the physical capacity of the drive?

[Lucky_Phil]

Thanks, changing that to 100% fixed the problem.

 

BTW, I also tried changing the allowed capacity to 500GB, but it snapped right back to 465GB. Any idea why Retrospect sets the allowed capacity to a figure significantly lower than the physical capacity of the drive?

 

This is due to the manufacture's method of calculating what 500 GB means, vs how a computer sees that "500 GB" ...

 

As explained here:

 

http://www.tweakandtrick.com/2013/07/lost-storage-space.html

[DavidHertzberg]

Thank you, Lucky_Phil. I should have known that, but I hadn't bought external drives for many years.

For those of the fellow-ignorant who don't have time to read his linked-to page (which actually doesn't take very long to read), the short version of his answer is:

For reasons of mathematical convenience and tradition, to computer people 1K does not mean 10**3 = 1000 but 2**10 = 1024. However for reasons of sales hype, disk drive vendors consider themselves to be ordinary metric system users instead of computer people, so to them 1K means 10**3 = 1000. That goes for all the multipliers of 1K, so what G-Tech calls a 500GB capacity disk drive is what computer people would call a 465GB capacity disk drive. Retrospect is designed to be used by computer people.

Not that I use tape drives any more, but I assume that tape drive vendors describe capacity using the same terms as disk drive vendors.

[MikeHutch]

Hi David,

 

Also, the disk directory also takes up disk space, so you'll never have the full capacity of the disk. After formatting the disk, you'll end up with about 95-97% of available space for you to use.