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  • On an AF disk with a 4096 byte physical sector size, partitions should start aligned to this size. I.e. the starting 512-byte sector number should be a multiple of eight. It's as simple as that.
    – Johan Myréen
    Commented Feb 2, 2018 at 18:00
  • Right, and as I pointed out when a multiple of 8 gets used, like a starting point of 2048s (like what I got with gParted), then the parted utility sees the disk as not optimal aligned, but only minimum aligned, and mkswap complains that my swap volume within the LVM is misaligned whether I stick with the 2048s or conform to parted's bizarre demand for a 65535s interval for optimal alignment. Just look at the sector parameters that the system drew. How can I even trust that those parameters are being correctly reported in the first place?
    – gluonman
    Commented Feb 2, 2018 at 18:20
  • My internal drive is an identically sized AF drive. The only difference is that it doesn't have a weird optimal IO size that warrants a sector interval outside the discrete space. It's optimal IO size is the same as it's minimum IO size of 4096, and it starts at 2048s, and parted thinks its partitions are optimal aligned. Hence, I'm wondering if the only reason my utilities are complaining about misalignments, and that parted wants me to use 65535, is because the optimal IO size is a wrong number. I think that's my best hypothesis atm. But I just want to be sure I'm actually optimized.
    – gluonman
    Commented Feb 2, 2018 at 18:25
  • 1
    The "optimal IO size" is just a hint of some sort, and 65535 is definitely not optimal to use as the number of 512 byte sectors to start a partition on. The GParted manual says: "Use MiB alignment for modern operating systems."
    – Johan Myréen
    Commented Feb 2, 2018 at 18:38
  • Okay. It's becoming established in my head that parted is just plain wrong in what it thinks is optimal (on both my Fedora and my Lubuntu), because the optimal IO size "hint" coming from this particular drive is throwing it off. Would you agree? I mean, I knew the numbers were weird, but I've trusted parted for years, and this is honestly the first time I've ever seen it throw alignment issues at me. So I should probably just go ahead and stick with 2048s intervals and ignore parted's complaints (and mkswap's, for that matter), right?
    – gluonman
    Commented Feb 2, 2018 at 18:45