OH! TIL! Apparently
reply contiguous fragmented
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PCIe 4.0 NVMe Read Speed ~5,000 – 7,000 MB/s ~80 – 250 MB/s
SATA 3.0 SSD Read Speed ~500 – 550 MB/s ~30 – 60 MB/s
> You are giving up virtually 0% to 3% of real-world performance. In daily development, media editing, and standard system use, defragmenting your SSD will yield no human-noticeable speedup.
Is it possible to determine which sectors are physically sequential given remapping for wear-leveling?
replyOtherwise the claimed defragmentation here is not actually resulting in sequential data.
You cannot directly inspect the degree of fragmentation, because it has less to do with being contiguous in the Logical Block Address (LBA) space and more to do with having been written at the same time. To properly defragment a file on a SSD, you pretty much need to sequentially re-write the whole file in one go, to a newly-allocated part of the drive's LBA space.
reply>Otherwise the claimed defragmentation here is not actually resulting in sequential data.
replyI haven't measured it but the SSD firmware should be able to look up where the next block is speculatively in order to be able to immediately start sending it if the host tries and read the next block (as opposed to a random one).
Prefetching applies to SSDs too, and that's generally sequential in some sense.
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