When copying data from one drive to another is it common to have slightly different file sizes or should they be exactly the same?

I’ve had them show up as slightly different. I think it may be due to different hard drive formatting or file storage issues.

The drives are the same brand of drive and the same file system Mac OS extended (though one drive I bought months ago the other is new). I am recopying the data right now to see if I can get them to match.

It can depend on how you have determined how a folder should be viewed ie, for images or music or general because “DLL is placed into that folder, by default and could change the volume. for example “Thumbs.dl”

@ actuallery

It’s the same computer reading the file sizes- does that matter then?

I’m not an expert, but I can point you in the direction to look if you want to research this further.

Generally, larger drives store files in larger “clusters” (think of it as “the right size box” for your file). So a file that takes 2 k on a smaller drive (with finer clusters), because it is under 2048 bytes in size (a pretty small file, that is), might take up as much as 4 k on a larger drive where the minimum cluster size is 4056 bytes.

There is also a difference in file system setups between (generally older) FAT32 systems and NTFS, at the drive level.

Removed by me because @CyanoticWasp already wrote what I was thinking

@CyanoticWasp -Thanks for response. Unfortunately, the drives are both the same exact size (500 Gb) and the same file system.

Should I not be using the finder and be using a Backup program? Is that any more accurate?

Probably just a difference in block sizes. I wouldn’t worry about it. If you just to want to make sure everything transferred you can use diff -r path1 path2 in the Terminal to check that everything made it across.

@blah_blah – I’ll try that. I’m not so terminal savvy- just type this into the terminal when the transfer is done and it will tell me? what should I be looking for as a response?

Adminstrative Tools > Disk Management. Click the drive to see how clusters are managed. Some drives, even though the same volume, DO have different cluster and block sizes if the brand name is different.

Also, Enable the option for viewing files. Explorer > Tools > Viewing Options. Show all files including system files, show extensions etc.. This will help you see what files are hidden.

@Actuallery

Unfortunately, there are a huge amount of items- if the items numbers match does that mean I’m OK? Same brand drive- an external Lacie- though I suppose they could have switched the brand of drive that they use.

blah-iMac:ScreenShots blah$ diff -rq /Volumes/Media/lyr /Users/blah/Desktop/lyr

Files /Volumes/Media/lyr/index.php and /Users/blah/Desktop/lyr/index.php differ

Only in /Users/blah/Desktop/lyr: untitled folder

blah-iMac: blah$

First line is diff -rq and the path two the folders we want to compare. to fill in the path in the Terminal you can just drag and drop folders from the finder. The second line is telling me that the file is different. It actually looks inside the text file. If you leave off the q flag it will tell you what exactly is different.

The third line is telling me there is a folder in one but not the other.

@blah blah- that’s a littel complex for me but I think I understand- let me give it a shot- first thing I write in the terminal is diff -rq then drag in the first path, then drag in the second right?

Thanks for your patience

little

Last login: Sun Aug 29 17:03:07 on console
Sarovars-Mac-Mini:~ ssb$ diff -rq /Users/ssb/Desktop/Compare\ folder\ 1 /Users/ssb/Desktop/Compare\ folder\ 2
Only in /Users/ssb/Desktop/Compare folder 1: .DS_Store
Only in /Users/ssb/Desktop/Compare folder 2: Ashoks remorse.m4a
Sarovars-Mac-Mini:~ ssb$

Correct?

@ blah blah Now if they are the same I should get no response, right?

Yes. If they are the same it doesn’t say anything.

Cool. That’s a helpful tip- thank you! Would you know what is the DS_ Store file by the way? Sorry, I’m trying to learn. Thanks so much.

They are just little files that keep track of how your icons are arranged. That is why one is kept in each folder. They store background images too. They are like a plist file for each folder. The period at the beginning of the file name is how OS X tells the Finder to not show them.

Using ls -a in the Terminal will show them. ls is the list command and the “a” flag will show hidden stuff.

Try ls -a ~ to see some of the hidden stuff in your user folder. It is best to never touch any of the hidden files. They hide them for a reason.

Gotcha- thanks. I just wanted to know why that was showing up as a difference in the files- it must be that the icons are arranged differently or something. Thanks!