Running a SMART check on my Librem 15v3 250GD SSD (a Samsung SSD 850 EVO M.2 250GB with firmware EMT21B6Q), I get a normalized value for the wear_levelling_count of 20.
I gather this is low, and I should be thinking of changing it. Can I wait till the value drops to 1, or should I look to change it now?
My understanding of SSD is that it is the delete/write operations that account for its wearing down. Most of my write/delete operations take place specific folders, such as downloads, temp and trash, as well as the /swap partition. Does it make sense to move these a cheaper secondary ssd, or even a hdd in order to preserve the main SSD’s life-time?
Not terribly so. It should start at 100 and work its way down to 0 during the nominal lifespan of the disk.
That is saying that it is 80% of the way through its nominal life but even then it is not a guarantee either that it will survive all the way to 100% or that it will die with certainty at 100%. Only you can tell us how quickly it is moving through its reported life.
Regardless of the disk’s life, you always do backups, right?
Whether you replace now or soon or very close to 0 depends on things like: how long it would take to get a replacement disk, how long to restore from backup, how long you can afford to be without that computer, what’s on the disk, whether you have another computer to use, whether the computer has more than one disk, …
Theoretically that shouldn’t matter because the point of wear levelling is to spread the erase load evenly across different pages of the disk (and also to use spare pages if a page becomes unusable on a write or perhaps unreliable on a read). This all happens completely invisibly to the operating system, behind the scenes in the SSD controller.
If you are not actually swapping then it isn’t really a problem but then you can get rid of the swap partition entirely.
If you are swapping a lot then maybe get more memory.
Somewhere in between yes maybe it would make sense to move swap to a different disk.