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.
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).