32 gig thumb drive = 26 gig?

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32 gig thumb drive = 26 gig?

I bought a bunch of 32 gig usb 2.0 thumb drives for lightweight portable storage. Also, I figured to use at least a couple for emergency boot/repair drives. Before, when I had done this with 16 gig drives, I reformatted them to Mac OS extended, journaled, GUID so I could boot my Intel Macs. Easy peasy. This time, however, with these 32 gig drives, the same process yields a 32 gig drive with 26 gig of usable space; somehow, nearly 6 gigs has been "allocated" (shows as a blue segment in the Disk Utility graph) and I can't figure out how or why or where. This did not happen with the smaller drives. (If I reformat back to the original FAT32, I get the use of nearly the entire drive - but then it's useless as a boot drive.) Help?

MacBook Pro (15-inch Late 2008), Mac OS X (10.6.8)

Posted on Aug 5, 2012 6:19 AM

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Answer 1

sig

Level 8

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Aug 5, 2012 8:11 AM in response to Richard Pini

By the time you format it and set up a 4 gb+ installer I guess that should drop it by 6 gb.

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Answer 2

b j t

Level 4

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Aug 5, 2012 8:35 AM in response to Richard Pini

This article also explains the different way that the drive space is calculated: http://support.apple.com/kb/TS2419

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Answer 3

Richard Pini Author

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Aug 5, 2012 12:58 PM in response to b j t

Thanks for the replies. I was curious because some small time ago I'd partitioned a couple of 16gig flash drives the very same way, and ended up with most of the 16 gigs available - nothing at all like the bite taken out of the 32s. (Plus, while poking at this, I discovered that if I partition the 32 gig drive into two 16 gig volumes, EACH of those gets the same 5-6 gig chunk stolen - clearly a losing game.)

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Answer 4

b j t

Level 4

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Aug 5, 2012 11:01 PM in response to Richard Pini

There is a formula for doing the math's that is explained in more detail in this Wikipedia article: http://en.wikipedia.org/wiki/Hard_disk_drive#Capacity.

I hope this gives you a better understanding of how the drive size is calculated.

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Answer 5

Aug 5, 2012 11:10 PM in response to Richard Pini

OK, I have a couple of SanDisk 32GB drives and they format to 32.02 GB. I just plugged one in to see the total capacity using Disk Utility. It may be due to the maker of the drive - who manufactured your USB flash drives?

Clinton

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Answer 6

Courcoul

Level 6

18,684 points

Aug 6, 2012 12:09 AM in response to Richard Pini

And, as you use it, be sure to empty the trash. Each volume has its own "trash bin" so to say, so if you dismount the thumbdrive and then do an Empty Trash, the junk in the thumbdrive survives since it wasn't around when bits were being blasted. Then, when you plug it back in, SURPRISE, trash magically reappears.

Last but not least, these being, well, drives, GB == Gigabytes are calculated as 10^9 = 1,000,000,000 bytes. Memory is measured in powers of 2 so gb == gibibytes which is 2^30 = 1,073,741,824 bytes.

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Answer 7

b j t

Level 4

3,698 points

Aug 6, 2012 12:23 AM in response to Courcoul

I thought I got away from having to do math like that when I left school :(

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Answer 8

Courcoul

Level 6

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Aug 6, 2012 12:26 AM in response to b j t

Mwahahaha!

👿

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Answer 9

Richard Pini Author

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Aug 6, 2012 4:14 AM in response to clintonfrombirmingham

These are SanDisk. And I do know about how drive size is measured, the new vs. the old terminology. Related to the "empty trash" suggestion, I went looking about and found a different suggestion for formatting the thumb drive - instead of using Disk Utility to "partition", just use it to "erase" - set the format to Mac OS and, magically somehow, I ended up with (almost) 32 gigs of usable space (in GUID too, so it can be used as a boot drive).

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Answer 10

Aug 6, 2012 4:17 AM in response to Richard Pini

That's how I use two of mine. I have one with Lion installed (and the "Install OS X Lion.app" in the Applications folder, and one setup the same with Mountain Lion. I can boot from both, use the OS X installer from both, etc. Mine are SanDisk as well. Got a deal on them through Amazon.

Clinton

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