HELP! Puzzling Black Magic Tests with 1 TB Samsung T7 Shield and m1 air

[Cory79]

Im getting the following speeds with Samsung 1Tb T7 Shield SSD and M1 MacBook Air 8GB (Ventura 13.4.1) running BlackMagic tests:


APFS (encrypted):

Connected to MacBook: ~750/750 MB/s

Connected via USB C Hub: ~230/180 MB/s



APFS (no encryption):

Connected to MacBook: ~680/680 MB/s

Connected via USB C Hub: ~680/570 MB/s



I don't know why encryption slows down the via the hub (Anker 10gbps) so much and it also makes no sense for encrypted to the faster than decrypted when connected directly to the MacBook (dropped by ~100 MB/s for both read and write). The drive is partitioned half for time machine and half for other files if that makes a difference (until I can get another dedicated time machine drive).

If posting this in another section would be more helpful, please let me know (I don't want to overcrowd the forum). This has been driving me crazy any help would be greatly appreciated!

 

[theorist9]

That is strange that the non-encrypted speeds are slower when the SSD is connected directly to the MBA. Are you comparing an encrypted partition to a non-encrypted partition? If so, it would be better to test the same partition encrypted and non-encrypted, to ensure there are no differences due to the partitions themselves.

Or if you don't have anything on the drive yet, wipe it and test the whole drive non-encrypted, then repeat after encryption.

Also, I don't know if this would have an effect, but it would probably be a good idea to give enough time for the encryption to complete.

Finally, you should re-run the tests with AmorphousDiskMark (free on the App Store) to see if you get qualitatively similar results.

 

[Cory79]

I did test the same volume from the same partition while ensuring to wait for encryption and decryption to finish fully. I have some time machine backups, but I don't think I have anything I need from them so I could consider wiping the drive. I'll test with AmorphousDiskMark first though.

 

[ChrisA]

Im getting the following speeds with Samsung 1Tb T7 Shield SSD and M1 MacBook Air 8GB (Ventura 13.4.1) running BlackMagic tests:


APFS (encrypted):

Connected to MacBook: ~750/750 MB/s

Connected via USB C Hub: ~230/180 MB/s



APFS (no encryption):

Connected to MacBook: ~680/680 MB/s

Connected via USB C Hub: ~680/570 MB/s



I don't know why encryption slows down the via the hub (Anker 10gbps) so much and it also makes no sense for encrypted to the faster than decrypted when connected directly to the MacBook (dropped by ~100 MB/s for both read and write). The drive is partitioned half for time machine and half for other files if that makes a difference (until I can get another dedicated time machine drive).

If posting this in another section would be more helpful, please let me know (I don't want to overcrowd the forum). This has been driving me crazy any help would be greatly appreciated!

Encryption may also compress the data so there may be fewer physical bytes to rad on a compressed volume. It would depend on the kind of data you have. Does Black Magic use compressible test data? It looks like it must.

The encryption itself is "free" and uses zero CPU time bcause there is speciazed hardware, like the T1 chip on older macs but now part of Apple Silicon.

Why slower with USB? The encryption hardware is combined with an SSD controller and might not be used for USB drives