I have a few SSDs of small capacities which I'd like to put to work, and imagined they could be useful for frequent backups.

At the same time my time capsule HDD stopped working after 5 years of duty.

Which leaves me wondering : Is there a way to indicate this kind of backup hierarchy where frequent change would be picked up by SSD, in order to :

  • be very fast
  • save strain on the HDD

in a way that, should one SSD fails, only the incremental changes would be lost, the weekly/slower moving backup would still be on HDD.

1 Answer 1


Yes, you can use multiple disks. No, you can't specify a different set of backup targets by disk and they all get all data, so your smallest disk needs to accomodate all data.

Though, you might be able to backup a full Time Machine config, alter it to trim out big volume directories, back up to SSD, restore full backup configs, backup to HDD, repeat. Seems more work than worth it.

And what happens if you run the small backup on your HDD by mistake? Will Time Machine try to reclaim space on things that it doesn't see as needing backup?

A quick and dirty rsync script to copy critical stuff to SSDs might work better.

  • I am not sure I get your question : the whole point is that the two (SSD,HDD) should be linked in the same way than snapshots are linked within TimeMachine. It's just that I would like the freshest ones (most frequently updated) to live where it's the fastest, and the oldest ones (less frequently generated) to live in a slow, (as) safe (as possible) storage.. My small SSD is not able to have one entire snapshot, but it can holds some snapshot differences
    – nicolas
    Commented Jun 20, 2018 at 14:53

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