Significant difference between "Size" and "Size on disk"?

There's a serious size difference between the Size of this folder and the "Size on disk". See below. I expect minor difference, but this is around a 1:3 ratio, 764mb vs 2.27GB.

The folder was copied from to a Flash / USB drive. On my C: drive, it's 772mb actual / 785mb on disk.

There is another folder on the Flash Drive that is similar and the measurement is very accurate. But while that one is 16gb, it's only 1500 files. This one, OTOH, does have a lot of files (16,000). Is each one gobbling some predefined chuck of Flash on this drive?

Thoughts?

You probably have a lot of files which are smaller than the filesystem's block size.

Say your filesystem's block size is 4K. A 1024, 2048 or 4096 byte file will equally consume a single block in order to store the file. The remaining unused space inside the block cannot be assigned to a different file. So even if a file is smaller than 4K, it will consume a minimum of 4K. There are minor exceptions when the file is a tiny number of bytes when NTFS will keep the data inside a directory block (and not take a 4K block).

If you have a number of massive files (ie. movie files), then the "wasted space" is very small relative to the entire file's overall length. But if you have lots of tiny files, a lot more half-filled blocks will be consumed on-disk. So your usable disk space gets drained really fast.

One solution is to reformat your drive with a smaller block size. Therefore, whenever the filesystem has to use a half-full block, you'll have more blocks left to use because they're sized closer to the most likely file size. The tradeoff is a smaller block size leads to a slower transfer rate, because it takes more reads or writes to pull the same total amount of data (more overhead).

Here's mine... no extensions, no email client, and my drive is set at 4K




C:\Users\user name\AppData\Roaming\Mozilla\Firefox\Profiles\xxxxxxxx.default-release

Thanks. I'll see if I can see the formatting and/or just reformat to a smaller block size. This is just backup, so speed isn't that much of an issue.

Levitate11 said:

Thanks. I'll see if I can see the formatting and/or just reformat to a smaller block size. This is just backup, so speed isn't that much of an issue.

Click to expand...

What is the block size? It looks fine on your C drive so if it is block size on the USB flash drive. It must be very large blocks. Typically, from what I know, USB flash drives don't have that big of a block size. It is probably that your flash drive has fragmented blocks. This can happen on flash since the blocks can contain partial data.

What is the capacity of the flash drive? If it is formatted as NTFS, you can TRIM it and that should take care of it. But it shouls have already. If this is what is happening and it is not NTFS, then garbage collection should eventually take care of it.

The cluster size of the SSD with NTFS (4KB) is different than the flash drive with FAT32 (8KB).



Default Cluster Sizes:

NTFS
* Up to ~2 TB: 4 KB (default)
* 16 TB to 32 TB: 8 KB
* 32 TB to 64 TB: 16 KB
* 64 TB to 128 TB: 32 KB
* 128 TB to 256 TB: 64 KB

FAT32
* < 8 GB: 4 KB (4096 bytes)
* 8 GB - 16 GB: 8 KB (8192 bytes)
* 16 GB - 32 GB: 16 KB (16384 bytes)
* > 32 GB: 32 KB (32768 bytes

Click to expand...

I tried other flash drives. Despite what the information above says the cluster size for all my flash drives (1GB, 16GB, 32GB, 64GB, 128GB) (all FAT32) was 8KB. Even the really small flash drive 32MB (FAT) has a 8KB cluster size.

My WinSxS directory is the other way round in terms of space usage.

Finally getting back to this:





Any ideas?

Default cluster size for a exFAT volume is determined by a sliding scale. For a 64 GB drive, it's normally 128K(!)

But you can check with PowerShell (block size reported in bytes):