On Mon 22 Oct 2018 at 19:41:09 (+0200), Pascal Hambourg wrote: > Le 22/10/2018 à 17:49, David Wright a écrit : > > On Mon 22 Oct 2018 at 14:42:09 (+0200), Pascal Hambourg wrote: > > > Le 22/10/2018 à 05:50, David Wright a écrit : > > > > > > > > Noted above. This is to give you partition alignment of 1MiB for > > > > efficiency. For GPT disks like this, I also add a 3MiB partition > > > > (giving me 4MiB alignment) set to "BIOS boot" which, like it says, > > > > allows it to be booted in legacy mode if ever required. > > > > > > Why do you need 4 MiB alignment ? > > > > As you probably know, I don't. > > No, I didn't know, so I was curious. You may use an SSD with an > uncommon 4 MiB erase block size. Less than one hour after I posted the > question, I read a post from someone who considered converting > partitions into LVM logical volumes without moving data and was > fortunate they used 4 MiB alignment, as LVM uses 4 MiB blocks > (extents) by default.
Sorry to make the assumption. For me, disks are spinning rust and SSDs are something for the future. Perhaps. If I'm fortunate. > > Is there any harm in always rounding up? > > It wastes space. > > > I'm just generous to Grub and its ilk. > > GRUB does not even need a MiB BIOS boot partition. AFAICS, the biggest > generated core image embedding all required drivers fits into 128 KiB. > > > When you read posts about > > partitioning, you realise there are some really stingy people out > > there. They would probably be calculating a size that squeezes it into > > the space before 1MiB. > > This is what I do when converting a disk from DOS/MBR to GPT. There is > plenty of space for a BIOS boot partition between the GPT partition > table and 1 MiB, and the BIOS boot partition does not need to be > aligned (no write performance issue). The ones I've converted were old/relatively small (≤2TB) and had the first partition starting at the traditional 63, so I'm repartitioning from scratch anyway. But I can't get worked up over the odd MB. I've seen big disks where the first partition starts at 2048 which is 8MiB for 4K sector size. Cheers, David.
