Stupid Question: Bootcamp and Fusion Drive

[Dorkington]

I've seen a few posts about the two, but not my specific one... sorry if it's discussed...

I have a 27" iMac with 1tb fusion drive.

In OSX, like it should, it's a 1tb drive.

I set up bootcamp, gave Windows a 128gb partition.

Now in OSX, my Mac OS drive is 983gb, instead of 878gb it "should" be, if 128gb were taken from it to give to Windows.

Any ideas what's going on?

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Followup:

Finder is showing my Mac OS drive size being 984gb
Disk Utility is showing my Mac OS drive size being 872gb

 

[Weaselboy]

Do you have Time Machine backups turned on? If you do, it makes hidden local snapshots. That space space is not included when you look at Finder but is included in Disk Util and this is normal.

You can briefly turn TM off then on again and it will erase this space.

 

[Dorkington]

Do you have Time Machine backups turned on? If you do, it makes hidden local snapshots. That space space is not included when you look at Finder but is included in Disk Util and this is normal.

You can briefly turn TM off then on again and it will erase this space.

Wouldn't that make my drive show less available than what should be correct, not more?

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To put my query in visual terms:

Finder (theoretically incorrect, since the logical 1tb drive is missing 128gb):

Disk Utility (theoretically correct):

 

[Weaselboy]

Wouldn't that make my drive show less available than what should be correct, not more?

Yes, you are correct and I was thinking completely backwards. Sorry for the confusion.

If you open Terminal and enter "diskutil list" without the quotes, that should show the volume sizes and maybe that will help decipher this. It is odd though.

 

[Dorkington]

Yes, you are correct and I was thinking completely backwards. Sorry for the confusion.

If you open Terminal and enter "diskutil list" without the quotes, that should show the volume sizes and maybe that will help decipher this. It is odd though.

So... I'm a bit confused...

Disk2 should be equal to disk1s2, but it looks like it's adding disk1s2 and disk0s2 (plus a few extra mb?)

I'm at a loss.

Everything, in use, is working correctly. I just believe finder is showing me 120gb more available than I actually have. Unless my "OSX" drive has messed up the fusiondrive, and is now a "stacked" logical drive, in that the SSD has files stored on it, and the hdd has separate files stored on it, instead of the same files being on both, technically.

(in fact, I'm confused as to why "disk2" exists at all, shouldn't it just be disk1s2?)

 

[Weaselboy]

Image

So... I'm a bit confused...

Disk2 should be equal to disk1s2, but it looks like it's adding disk1s2 and disk0s2 (plus a few extra mb?)

I'm at a loss.

Everything, in use, is working correctly. I just believe finder is showing me 120gb more available than I actually have. Unless my "OSX" drive has messed up the fusiondrive, and is now a "stacked" logical drive, in that the SSD has files stored on it, and the hdd has separate files stored on it, instead of the same files being on both, technically.

(in fact, I'm confused as to why "disk2" exists at all, shouldn't it just be disk1s2?)

I think you are in good shape and Disk Util is just reading wrong because of the Fusion/Bootcamp combo.

That Terminal output is normal. Disk2 is not a real drive.... it is your virtual 983GB Fusion drive created by 871GB disk1s2 and 121GB disk0s2 added (fused) together.

I believe this is just a bug in DU, because that Terminal output adds up exactly.

 

[Dorkington]

I think you are in good shape and Disk Util is just reading wrong because of the Fusion/Bootcamp combo.

That Terminal output is normal. Disk2 is not a real drive.... it is your virtual 983GB Fusion drive created by 871GB disk1s2 and 121GB disk0s2 added (fused) together.

I believe this is just a bug in DU, because that Terminal output adds up exactly.

I was under the impression that fusion drive didn't add the SSD and HDD, but rather the SSD 'cloned' the 128gb of most frequently used data on the HDD. Have I been misunderstanding this the whole time?

 

[Weaselboy]

I was under the impression that fusion drive didn't add the SSD and HDD, but rather the SSD 'cloned' the 128gb of most frequently used data on the HDD. Have I been misunderstanding this the whole time?

Yep... you have been misunderstanding. The OS sees them both as one, big drive and it tries to move the most frequently uses bits to the SSD when possible.

Pretty good in depth article here explaining how it works.

 

[Dorkington]

Yep... you have been misunderstanding. The OS sees them both as one, big drive and it tries to move the most frequently uses bits to the SSD when possible.

Pretty good in depth article here explaining how it works.

AH HA!

Well I feel dumb now.

Could have sworn my original drive was 1TB, but I'm guessing it was 1.1TB and yeah...

*lurks back into the darkness*

Thanks!