Computers & Electronics

Why the HDD Size Difference - Advice

  • Last Updated:
  • Jan 19th, 2018 1:44 am
[OP]
Deal Addict
Aug 25, 2006
3675 posts
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Why the HDD Size Difference - Advice

So I have 2 x 3TB Toshiba Harddrives.

0. Right clicking properties inside File Explorer of each Drive letter show: Capacity to be 2.72 for both drives.

1. Windows Explorer shows Drive 1 = 176 GB Free of 2.72 TB
2. Windows Explorer shows Drive 2 = 288 GB free of 2.72 TB

3. Based on above, Drive 2 is not as full as Drive 1... but...
4. I am actually using Drive 2 to do a full backup of Drive 1 so... Drive 2 should be either equal or more full since the backup software does not delete any files if it only exists in the destination (Drive 2).

5. Selecting all files and folders on Drive 1 then right clicking to >> Properties show: 2.34 TB used
6. Selecting all files and folders on Drive 2 then right clicking to >> Properties show: 2.37 TB used

7. So why would Properties of selected files and folders show similar TB used (2.34 vs 2.37) but free space shows 176 GB vs 288 GB (about 110 GB difference)?

What is causing this discrepancy?
13 replies
Sr. Member
Dec 14, 2004
840 posts
119 upvotes
Waterloo
My first reaction is its related to hidden files.

How are you backing up the drive? What tool or are you just copying files over?
What type of drive is the source drive? Data only? Boot drive?

In theory it could be files sitting in the recycle bin. Maybe it's a restore point system file. I would grab a good file system analyzer to do a compare.
Deal Expert
Aug 2, 2004
33521 posts
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East Gwillimbury
Sounds like drive 1 is a boot drive.

A boot drive has hidden files and I believe there is a 100 Gig hidden partition used by Windows
Deal Expert
Mar 23, 2004
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Gee wrote: Sounds like drive 1 is a boot drive.

A boot drive has hidden files and I believe there is a 100 Gig hidden partition used by Windows
I think it's actually 100MB but yeah that^. Can also be more than one hidden partition on the boot drive.
Deal Expert
Aug 2, 2004
33521 posts
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East Gwillimbury
ES_Revenge wrote: I think it's actually 100MB but yeah that^. Can also be more than one hidden partition on the boot drive.
You're right. Reflex on my part.

The delta is probably due to the page file
Last edited by Gee on Jan 18th, 2018 11:53 am, edited 1 time in total.
[OP]
Deal Addict
Aug 25, 2006
3675 posts
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Great insight for troubleshoting. Let me reply below.
mre wrote: My first reaction is its related to hidden files.

How are you backing up the drive? What tool or are you just copying files over?
What type of drive is the source drive? Data only? Boot drive?

In theory it could be files sitting in the recycle bin. Maybe it's a restore point system file. I would grab a good file system analyzer to do a compare.
I have selected "Show hidden files, folders, and drives" and de-selected "Hide extensions for known files types". No difference.

Recycle Bin is empty still no difference.

Using SyncBack Free to run all backups. These are all secondary drives, not a boot drive.
Gee wrote: Sounds like drive 1 is a boot drive.

A boot drive has hidden files and I believe there is a 100 Gig hidden partition used by Windows
Neither are not boot drives. Used Disk Management to check and only see 1 partition on both drives.
ES_Revenge wrote: I think it's actually 100MB but yeah that^. Can also be more than one hidden partition on the boot drive.
The crazy thing is, I have opened up 2 instances of File Explorer in Windows 10 and selected each folder >> properties and the usage shows each folder (the same one on separate drives) as identical. Just that File Explorer is not showing the same amount of free space. Crazy gremlins right?

What else could it be?
Deal Expert
Aug 2, 2004
33521 posts
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East Gwillimbury
bowmah wrote: What else could it be?
Open up Power Shell and run chkdsk on each drive.

It will give you the total files on each drive. Make sure it matches

Other than that. The only other thing I can think of is the sector size. If drive two is older, it may use 512 bytes per sector instead of the newer 4k sectors. But I doubt it since you mentioned these are identical 3 Terabyte drives
[OP]
Deal Addict
Aug 25, 2006
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Gee wrote: You're right. Reflex on my part.

The delta is probably due to the page file
I have always set C drive (SSD) to be the pagefile drive. So no pagefile set for the Toshibas. Good direction though.
Deal Expert
Mar 23, 2004
28721 posts
9171 upvotes
bowmah wrote: The crazy thing is, I have opened up 2 instances of File Explorer in Windows 10 and selected each folder >> properties and the usage shows each folder (the same one on separate drives) as identical. Just that File Explorer is not showing the same amount of free space. Crazy gremlins right?

What else could it be?
You know what's funny... I had a very similar problem recently when I cloned two m.2 drives, on SATA and one NVMe. The 256GB NVMe drive was going on to the 128GB SATA drive. There was far less than 128GB on the drive so no problem to clone. This is a drive cloning mind you as well. The odd thing is when the cloning was done the original drive had more data on it, according to the main pie graph in drive properties, something like 5-10GB (can't remember now) more--i.e. the original drive seemed to have more data than the cloned one. I could not, for the life of me, figure out what that data was because if I selected all folders and then properties and it added up all the files that way, they were identical in size.

The reason I was doing this is because I was building a new system with the NVMe drive. Now I'm not one of those "I lost my data oh noes the world is ending!!1!" type people, lol. So what I did in the end was I just said "eff it" and went ahead and forgot about it and just re-partitioned the NVMe drive and did a new install on it lol. I'm not really "missing" any files from the cloned drive now...that I know of...and honestly I couldn't care less if I lost something as they're just computer files (and these are just local-machine files all my real files are on NAS which is also backed up).

I did kind of look at it sideways a while but I couldn't easily figure out what was going on. Because they were different size drives I couldn't compare the partitions directly. The partitions had different amounts of used data though, which was puzzling. But the direct, visible, file count came out exactly the same (and yes all my machines show hidden files, so it wasn't like any of those were left out of the count). My last thing I did before just forgetting about the whole thing was I did an old-skool command prompt--> dir /a/s and once again the counts were exactly the same. So I really don't know what was up with that but I didn't care so that was that. I can understand how this may be a problem for you and I hope you can figure it out because I'd also like to know just for reference.
[OP]
Deal Addict
Aug 25, 2006
3675 posts
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ES_Revenge wrote: So I really don't know what was up with that but I didn't care so that was that. I can understand how this may be a problem for you and I hope you can figure it out because I'd also like to know just for reference.
It's funny and comforting to know that others have also experienced this odd space reporting issue. Even funnier that someone else tried the same select folder and add up all file sizes as a double check! lol

There is not much else I can do without wasting more time on this so the likelihood of finding the culprit is unlikely. If I do one day find the issue, I will post back. Time to put this baby to bed and wait for the 8TB red to arrive! I am using RED's in a PC for backups and duplication. Crazy or thumbs up?
Deal Addict
May 26, 2002
1850 posts
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Size difference is due to Shadow copies. Pretty much every backup software uses shadow copy to do snapshoting. Windows also use shadow copy for system restore points and previous versioning. You won't see the used space from file explorer. You can Google how to view shadow copies.

-LeeBear
[OP]
Deal Addict
Aug 25, 2006
3675 posts
966 upvotes
LeeBear wrote: Size difference is due to Shadow copies. Pretty much every backup software uses shadow copy to do snapshoting. Windows also use shadow copy for system restore points and previous versioning. You won't see the used space from file explorer. You can Google how to view shadow copies.

-LeeBear
Interesting. I am pretty sure I have disbaled shaw copy in my Win 10 but I will check again later.
[OP]
Deal Addict
Aug 25, 2006
3675 posts
966 upvotes
LeeBear wrote: Size difference is due to Shadow copies. Pretty much every backup software uses shadow copy to do snapshoting. Windows also use shadow copy for system restore points and previous versioning. You won't see the used space from file explorer. You can Google how to view shadow copies.

-LeeBear
Looks like Windows 10 has File History and not Shadow Copy. Mine is not even enabled. Anyone else have any ideas on why the drive reports different free space?
[OP]
Deal Addict
Aug 25, 2006
3675 posts
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ES_Revenge wrote: ...I hope you can figure it out because I'd also like to know just for reference.
ok, found the issue and got the drives to show the proper amoutn of free space. It was eaten up with Restore Points. I have C Drive running Restore points and have disabled all other drives from using it. Not sure how a few HHD's have quite a bit of space being used for System Restore. Had to click on each drive and click on Configure to see the old restore points disk usage. Not sure if it was used up before I disabled System Restore on these drives or if C Drive is dumping system restore files to those drives in Win 10. Either way, I have deleted all Restore Points from no C drives and got back a ton of free space.

Happy camper now.

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