Upgrading an M4 Pro Mac mini's storage for half the price

The article speculates on why Apple integrates the SSD controller onto the SOC for their A and M series chips, but misses one big reason, data integrity.

About a decade and a half ago, Apple paid half a billion dollars to acquire the patents of a company making enterprise SSD controllers.

> Anobit appears to be applying a lot of signal processing techniques in addition to ECC to address the issue of NAND reliability and data retention. In its patents there are mentions of periodically refreshing cells whose voltages may have drifted, exploiting some of the behaviors of adjacent cells and generally trying to deal with the things that happen to NAND once it's been worn considerably.

Through all of these efforts, Anobit is promising significant improvements in NAND longevity and reliability.

https://www.anandtech.com/show/5258/apple-acquires-anobit-br...

> The article speculates on why Apple integrates the SSD controller onto the SOC for their A and M series chips, but misses one big reason, data integrity.

If they're really interested with data integrity they should add checksums to APFS.

If you don't have RAID you can't rebuild corrupted data, but at least you know there's a problem and perhaps restore from Time Machine.

For metadata, you may have multiple copies, so can use a known-good one (this is how ZFS works: some things have multiple copies 'inherently' because they're so important).

Edit:

> Apple File System uses checksums to ensure data integrity for metadata but not for the actual user data, relying instead on error-correcting code (ECC) mechanisms in the storage hardware.[18]

* https://en.wikipedia.org/wiki/Apple_File_System#Data_integri...

You can do this yourself in userspace if you really want it:

https://git.eeqj.de/sneak/attrsum

I use zfs where I can (it has content checksums) but it sucks bad on macOS, so I wrote attrsum. It keeps the file content checksum in an xattr (which APFS (and ext3/4) supports).

I use it to protect my photo library on a huge external SSD formatted with APFS (encrypted, natch) because I need to mount it on a mac laptop for Lightroom.