not enough disk space

Posts: 5 · jan.stritesky 23 Jul 2023, 14:07

Hello,
I want to synchronize two identical disks, each 6TB in size. One is almost full (there is 142GB of free space). The other is completely empty, cleanly formatted. Both drives have the bins drained. When trying to copy, FreeFileSync shows 5.50TB of space occupied, more than the disk size shown in Windows Explorer. I also tried turning off the safe copy feature, but this had no effect on the size of the data being copied.
Thank you for your help.
Regards
Jan

Posts: 4867 · xCSxXenon 23 Jul 2023, 14:13

https://freefilesync.org/faq.php#explorer-mismatch
They could have different block sizes too

Posts: 5 · jan.stritesky 23 Jul 2023, 14:29

The block size is the same for both drives - 512B.

Posts: 4867 · xCSxXenon 23 Jul 2023, 14:43

I was referring to "Allocation unit size" as Windows calls it

Posts: 5 · jan.stritesky 23 Jul 2023, 15:45

The discs are formatted identically - see attachment. And they are exactly the same type. One has data on it and cannot be copied to the second disk.

Posts: 4867 · xCSxXenon 23 Jul 2023, 16:06

In the properties of the G: drive, what is the 'size on disk'?
Also, you may not have followed the link I posted, but there are some possibilities in there

Posts: 5 · jan.stritesky 23 Jul 2023, 18:30

The G drive properties do not specify the size on the disk. I followed the link you posted, but found no solution.

Posts: 4867 · xCSxXenon 24 Jul 2023, 13:43

Run WizTree on that G: drive. Then we can confirm if Windows is off its rocker again

Posts: 1202 · therube 24 Jul 2023, 15:27

two identical disks

FreeFileSync shows 5.50TB of space occupied, more than the disk size shown in Windows Explorer

Thinking the first is incorrect.
Thinking the second is correct.

While the may both be "6TB", while they may both be the same "brand", there is difference between the two. (At the least, total sectors is different.)

And the latter message is also likely correct? (May also be correct?)
You're looking to copy "everything" from G: to F:, but "everything" on G: takes up more (albeit very little more) room then there exists in free space on F:.

Exclude "something" from G: (enough such that FFS no longer complains) & your copy should then proceed (without warning). (Or, you could say "ignore" to that message, & "all" will copy - but not entirely all, something [theoretically] will not fit.)

And that said, it is still kind of weird, because G: is not full, using only 5.31 GB of space (which theoretically is less then the available free space on F:).

I suppose your file sizes could also be playing in. Cluster size is 4096 bytes, so a file of 1 byte will actually require 4096 bytes of disk space (1 cluster) [slack space] [& aside from the case where small sized files may end up in the MFT [is it?] instead].

Looked at another way...

(G:) 1465110015 clusters - 37399889 = 1427710126 clusters in use

(F:)                                  1465055111 free clusters

(so theoretically G: should fit on F:) ;-)

Posts: 7506 · Zenju 25 Jul 2023, 12:05

FreeFileSync has a tree view panel on the lower left ("Overview"). You can use it to find out where the additional file content is coming from. (Most likely it's hard links, or sparse files)

Posts: 5 · jan.stritesky 1 Aug 2023, 14:29

Hello,
there are no sparse files or hard links on the source drive.
The target disk is RAID1 - mirror (two same disks as the source disk), I understand that RAID has some overhead, but it should not be in the order of dozens of GB. There is 140GB free on the source disk.
I copied the source disk from another disk with HTFS+ file system using Tuxera (switching from Mac to PC).
I also tried changing the cluster size to 1024 bytes, but that doesn't solve the problem. There are rather large files on the disk. Maybe a hundred files of 1KB size.
Regards.
Jan