en/computer/partition pregapWEBlog -- Wouter's Eclectic Bloghttps://grep.be/blog//en/computer/partition_pregap/WEBlog -- Wouter's Eclectic Blogikiwiki2014-03-01T13:42:06ZRecommendationhttps://grep.be/blog//en/computer/partition_pregap/comment_2181/Paul Tötterman2014-03-01T13:42:06Z2013-08-05T11:06:26Z
I was hoping to see a recommended size or requirement for using grub2.
Why so big?https://grep.be/blog//en/computer/partition_pregap/comment_2182/Steven C. (steven@pyro.eu.org)2014-03-01T13:42:06Z2013-08-05T13:50:34Z
<p>Why wasn't 32 KiB enough anyway? Probably the core.img includes more modules than strictly necessary; I'd have looked to reduce its size. /boot being within LVM+RAID is probably a factor, as is perhaps the filesystem being used (e.g. the btrfs module is more than 2x bigger than ext2).</p>
<p>There may be a way to convert to a GPT disklabel in-situ, within the 63 sectors at the beginning of the drive (and needing a similar space at the end of the disk). If there is also space to create a small GPT BIOS Boot Partition anywhere, you could write the core.img there instead.</p>
<p>And finally, there's always the grub-legacy package...</p>
https://grep.be/blog//en/computer/partition_pregap/comment_2183/Bob Proulx (bob@proulx.com)2014-03-01T13:42:06Z2013-08-05T19:44:27Z
Your alternative suggestion is how I have fixed this problem for me before. When migrating from a 2x 1T disk RAID1 to a 2x 2T disk RAID1 with AF partitions and larger sectors. Usually I would degrade the raid, add the new disk, then sync the raid. Couldn't do that due to the need to change to AF 4k sectors. Because I had LVM available I simply added the 2T disks, partitioned it for AF, created the RAID1, then used pvmove as you described to migrate the data. Then run grub-install onto the new disks. The machine was up and online through the migration. The only downtime was the reboots to add the new 2x 2T disks initially and again later to boot to the new disks in the new config afterward. Having LVM made something difficult into something mostly pretty easy.
Alternativehttps://grep.be/blog//en/computer/partition_pregap/comment_2184/Elessar (tanguy+grep.be@ortolo.eu)2014-03-01T13:42:06Z2013-08-07T08:53:44Z
<p>I thought the default was to have the first partition start at the beginning of the first cylinder, thus leaving most of the zeroth cylinder as a pre-gap usable to store GRUB's core image.</p>
<p>Now, I prefer partitioning as GPT and defining a small BIOS Boot Partition to store GRUB's core image. Or an EFI System Partition when I boot in UEFI, of course.</p>