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charcircuit • today at 3:49 AM • 3 replies • view on HN

Sequential reads are faster for SSDs. As long as defragmentation is reducing the chance of doing a random read, it is beneficial.

Replies

socalgal2 • today at 5:39 AM

OH! TIL! Apparently

                                contiguous              fragmented
    -------------------------------------------------------------------
    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
Still, given SSDs have a lifespan and given few of my files are that large, I think I'm personally okay without defragmenting. Those numbers are impressive but, most of 10s of thousands of files are source code text files. Asking online what the real-world loss is from not defragmenting

> 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.

__d • today at 4:33 AM

Is it possible to determine which sectors are physically sequential given remapping for wear-leveling?

Otherwise the claimed defragmentation here is not actually resulting in sequential data.

➕ show 2 replies
Groxx • today at 4:50 AM

Prefetching applies to SSDs too, and that's generally sequential in some sense.