leaving unused space on SSD (to increase lifetime)?

Question

I am reading that SSD need to have some "garbage collection".

For an SSD which would be the main device of a Linux desktop (the precise model I bought is Samsung SSD 970 EVO M2 - 2Tbytes), does it make sense to leave a small part of it unused?

I'm thinking of e.g. partitioning that SSD such that 2% of it remains in an empty Linux partitioning.

My dream is that by leaving some unused space, I might improve the life time of that SSD (because the firmware inside it would "rotate" that unused space). Does that make sense?

But I am not a hardware guy at all, so I could be very wrong.

This could be a related question (on "unix&linux").

Answer 1

SSD use TRIM to avoid too many write operations that will shorten its life expectancy. However, as TRIM works on much larger blocks than are allocated by the operating system for sectors, there can be a problem when TRIM requires empty space for relocating sectors from partially-empty blocks.

For this reason, SSD manufacturers practice Over-Provisioning, which is extra space that the SSD can use but the operating system cannot allocate. The SSD firmware will also do Garbage Collection to compact used space and free as much space as possible.

In spite of Over-Provisioning, it is counseled to leave more free space on the SSD. The numbers mentioned vary between 10% to 25%, but there are absolutely no studies that show an optimal number. In short, these numbers are only theoretical guesses.

I would still think that 2% is a bit low, as 10% was the lowest that I ever saw mentioned in the articles that I have encountered.

For more information I would recommend the article The SSD Anthology: Understanding SSDs and New Drives from OCZ and especially the section "Putting Theory to Practice: Understanding the SSD Performance Degradation Problem".