Safe to turn off antivirus if drive previously scanned?

[wwcanoer]

Is it safe to turn off antivirus when the drives were previously scanned by antivirus program?

i.e. When Duplicate Cleaner is performing MD5 (or binary) calculations on the contents of a file, is the file being opened in a way that a virus in it could be run? My impression is that anti-virus scanners don't "open" every file but Duplicate Cleaner could (or will) "open" many more of them. Does this create a risk if no anti-virus software is running during the Duplicate Cleaner operation?

Windows Defender significantly slows down file transfers by Teracopy and Syncovery. I assume the same for Duplicate Cleaner but have not tested it yet.

Why: Antivirus significantly slows down the copying of files. (by 3x)
Copying a 230GB folder from nvme Samsung 970 EVO Plus 2TB to nvme Lexar NM790 4TB:
260GB 268,000 files 14,000 folders

Windows Explorer: 8 minutes
Syncovery with Windows Defender active: 18 minutes
Syncovery with Windows Defender inactive: 6 minutes

Testing a smaller folder with Explorer vs Teracopy (with verification turned off) gave an even bigger difference between the methods.

My plan: Overnight, I perform an hours-long virus scan of all drives. In the morning, I turn off the internet and antivirus so that I can work on deduplcating and consolidating the drives without being slowed down by the antivirus.

(Note: Between each test I delete thed Syncovery profile so that no data is kept. The 230GB folder is synced to an empty one. When AV is active, it uses a lot of CPU and disk activity as seen in Performance Monitor.)

[wwcanoer]

Syncovery's author says that its safe to turn off antivirus because the file is read but no way for a virus to run. I assume the same is true for Duplicate Cleaner but would like confirmation.

I'll do the same style exclusion for Duplicate Cleaner:

Add the Process Exclusion: C:\Program Files\Syncovery\*
in Win 10/11 Windows Defender:
Virus & Threat Protection > Manage Settings > Exclusions > Add or remove exclusions > Process >

I now see that on one computer I already have an exclusion for C:\Program Files\FreeFileSync\Bin\* that must have been automatically added or approved by me because I didn't do it manually. (I use Syncovery for syncing but was looking to visually compare folders side by side.)

Now Syncovery only took only 3:41 to copy 230GB from 4TB Lexar to 2TB Evo. Wow!

(I'm burning up my SSD lifetime but understanding this will save me a lot of time! Despite the Lexar being dramless, it's performing very well and not getting as hot as the Evo but the temperature reading just became flaky (bouncing around).

[DigitalVolcano]

It should be OK - the program just reads the file as a stream of bytes (assuming you are hashing). It doesn't execute the file.

[wwcanoer]

Thank you for verifying that!

Test folder: 230GB 268,000 files 14,000 folders

Duplicate Cleaner - create virtual folder using MD5:
with Windows Defender active: 35 minutes
with Windows Defender inactive: 11 minutes

Windows Explorer - copy folder from nvme drive 1 to nvme drive 2: 8 minutes

Syncovery - copy folder from nvme drive 1 to nvme drive 2:
with Windows Defender active: 18 minutes
with Windows Defender inactive by manually turning off: 6 minutes
with Windows Defender inactive by excluding process: 4 minutes

Hp EliteDesk 800 G4 TWR WKS i7-8700 Win 11
nvme drives: Samsung 970 EVO Plus 2TB & Lexar NM790 4TB