More storage space used than I have?

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More storage space used than I have?

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  1. Windows
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For example, let's take the ActiveBackupforBusiness shared folder which houses two folders in it, @ActiveBackup and ActiveBackupData. Neither folder is using compression. In File Station, right clicking ActiveBackupData and selecting properties shows it's size as 11.08TB. This is the same that shows viewing that folder in windows explorer from my main PC.

My NAS is running 2x12TB Ironwolfs in SHR which provides 10.5TB of usable storage (10.9 shown in Storage Manager Drive Size) which I'm using for ActiveBackup, synology photos and a plex media server. Just the separate Media folder itself is using over a TB of data. Going to Storage Manager shows I'm using a total of 2.7TB with 7.8TB free for the single volume I have.

Why does File Station or windows explorer show incorrect Size/Used amounts for this folder? How am I to trust the size reported for any folder?

It doesn't. Under storage it shows a data reduction ratio of 1.43x but I don't see it's used space listed.

I think it's just this folder that shows this behaviour. It may be that under folder properties it's calculating the amount of space that would be used up if each time a backup was performed it stored every file again instead of linking files that remained unchanged from the previous backup.
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The img files aren’t really that big. The OS is showing the uncompressed image size not actual size used. Nothing to do with ABB compression.
Each file in an image may make a new file (if it's changed from the last backup) or may just point to the file that was created during a previous backup (if the file didn't change), correct?

So my thinking is that since the majority of files in future backups don't change, then most of files in those images are just "pointing/linking" to a file previously saved and not an "actual" separately saved file. This leads me to also think that the storage size displayed under folder properties does not take that into account.

Something like this (but for every single file in a backup).

backup1 - Actual File 1
backup2 - Link to file 1
backup3 - Link to File 1
backup4 - Actual File 1a (File 1 that was changed after backup3)
backup5 - Link to File 1a

The actual space used is 2 files (file 1 and file1a) but the properties shown under properties counts the space of 5 separate files (even though 3 of them are just links to the 2 actual files).

This is my thinking and I may be wrong, but it would explain why you would have folder properties showing more space used than what's actually available. If I am wrong or missing something additional, please correct me and add info as I'd really like to understand everything that's going on to get to the numbers it shows you.
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It doesn't. Under storage it shows a data reduction ratio of 1.43x but I don't see it's used space listed.
You can see how much space is being taken by ABB's storage, just scroll down Overview.

Or in Storage hover over Data Reduction Ratio's blue 'i'.

This will be the amount that the shared folder you use for ABB is pretty well using, unless you are also taking snapshots too (using Snapshot Replication). But the file system report of adding up the files it see isn't correct when it includes what it thinks is each img file. Also remember there can be some deduplication in Btrfs file system too. I would just take it that the size after reduction is what's being used.

If you run Synology Drive then there's a database that's not accessible from the DSM web interface. This is used for maintaining versions of Drive managed content.


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