Timeline for Trouble figuring out optimal alignment of multiple partitions on a 931.5 GiB external Advanced Format HDD while in Linux
Current License: CC BY-SA 3.0
13 events
| when toggle format | what | by | license | comment | |
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| Jul 26, 2019 at 4:14 | answer | added | McDull Hall | timeline score: 1 | |
| Feb 2, 2018 at 19:36 | comment | added | gluonman | I honestly have no idea, other than just guessing that it's complaining because it's confused about sector parameters for the same reason that parted is. Because the optimal IO size is a bad hint, as you mentioned earlier. But it is still concerning to move forward without absolute confirmation. I still somewhat feel like I'm just guessing that parted and mkswap are calculating incorrectly because of a bad hint. But you have helped direct my suspicions. | |
| Feb 2, 2018 at 19:22 | comment | added | Johan Myréen | Looks fine to me. But why would mkswap complain? | |
| Feb 2, 2018 at 19:19 | comment | added | gluonman | Alright. So to reach a conclusion, would you agree with the following approach on my part? I use a 2048s interval, and parted will complain that it's minimum but not optimal (it wants 65535), but I'm going to ignore those complaints because the optimal IO size is a crappy hint. fdisk will be happy, but mkswap will give a warning, but I'll ignore that too. And while I'm probably fine not worrying about my partition endings, I'll be eliminating the most number of possible future issues by making sure my partitions end on a sector rounded to 2048, similar to the starting point. Does that work? | |
| Feb 2, 2018 at 18:54 | comment | added | Johan Myréen | I guess the end alignment doesn't matter so much, but the file system might align itself to some nice round number of its liking, so you may end up losing even more disk space. This of course depends on the file system. | |
| Feb 2, 2018 at 18:47 | comment | added | gluonman | Should I also be worried about where my partitions end? Does it need to end on a value x where x mod 2048 = 0? Or is it perfectly fine to have a small gap in-between certain partitions? | |
| Feb 2, 2018 at 18:45 | comment | added | gluonman | 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? | |
| Feb 2, 2018 at 18:38 | comment | added | Johan Myréen | 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." | |
| Feb 2, 2018 at 18:25 | comment | added | gluonman | 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. | |
| Feb 2, 2018 at 18:20 | comment | added | gluonman | 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? | |
| Feb 2, 2018 at 18:00 | comment | added | Johan Myréen | 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. | |
| Feb 2, 2018 at 17:18 | review | First posts | |||
| Feb 2, 2018 at 18:24 | |||||
| Feb 2, 2018 at 17:13 | history | asked | gluonman | CC BY-SA 3.0 |