Max (max@a.com) on 1/25/11 wrote:
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>gallier2 (gallier2@gmx.de) on 1/25/11 wrote:
>---------------------------
>>So, sorry that in the end I answered my question myself, but thinking about the
>>problem from the firmware side made me realize that Linus is right: TRIM is more
>>than useless, adding complexity and overhead for something the firmware already has to do.
>
>TRIM is only useless if the drive is 100% full 100% of the time. It's useful to
>have free blocks, but it's also useful to be able to use the full capacity.

It seems to me that it also useless when
a) FS manages free logical blocks in LIFO manner (which seems to be the only logical option anyway).
b) Used space rarely shrunk by more few per cents of total volume and the average trend is up.

>In a
>way, TRIM makes the drive variable size. To the filesystem it's fixed size, but
>internally the managed size is determined by the free space.
>
>Max

I have another question. Is TRIM feature future-proof?

1. Can we assume that in the future SSD volumes will grow faster than the NAND sector size?
2. Can we assume that, due to power limitations if nothing else, sustained write throughput of SSDs will grow slower than their volumes?
3. Can we assume that reserved space will remain at 7% or more?
4. Finally, can we assume that FS block size will never be smaller than it is now and will most likely grow by factor of 4 or 8 in the near future?

If the answer is "yes" to all four questions then it effectively means that TRIM is not future-proof. Usefulness of TRIM, even in best case for it, will be greatly reduced over the time.