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I'm well-versed in manually-partitioning for RAID0 or RAID1, but only with BIOS, and I would just give /sda an extra 1MB partition for GRUB.

With UEFI installed, however, I am not sure what to do with the ESP partition: just set aside 500MB on /sda or should I RAID0 250MB each on /sda and /sdb?

EDIT: I am using a 2012 Mac mini, which does not have a hardware RAID card. Your results may vary.

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You should definitely not use striping (RAID 0) or any more advanced RAID level (like RAID 5) with the ESP. At first glance, you might think that RAID 1 (mirroring) should be OK; however, if something outside of Linux (like an EFI boot loader) were to write to the partition, that would result in inconsistencies that would cause problems. It'd be hard to rule out the possibility of something like that happening. Thus, I'd be reluctant to use RAID 1 on an ESP. If you want some redundancy, you could create a second ESP on your second disk and manually sync them every now and then -- perhaps even automatically via a cron job or a startup script.

All of this assumes Linux software RAID, of course. If you've got a hardware RAID card, the EFI will see the RAIDed drives as a single device, so there's no issue. With a motherboard-based software RAID, you'd need to check to see if the firmware understands the RAID setup.

  • Thanks for the reply! I mirrored (RAID1) the ESP partitions on each drive, but that was unbootable post-installation (just a black screen). – jimmyco2008 Dec 15 '15 at 13:35
  • @RodSmith I mostly agree, but I don't see a need for syncing the ESP frequently with Grub, the config file on the ESP is only 3 lines and chainloads the main cfg file in /boot: search.fs_uuid $my_uuid root hd0,gpt2 \n set prefix=($root)'/boot/grub' \n configfile $prefix/grub.cfg so mirroring it once each release upgrade should be sufficient? – LiveWireBT Dec 15 '15 at 13:43
  • GRUB updates get pushed out every now and then, so there's always a chance that a cloned ESP will be out of sync with the current one. This risk increases if you have multiple OSes or boot loaders installed. A tool like rsync should have very low overhead if there are no changes, so there's little point in not using it to keep a clone up to date. – Rod Smith Dec 15 '15 at 14:31
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No, you do not RAID the ESP across multiple drives. Doing so will result in a failed installation (un-bootable). Just treat the EFI System Partition (ESP) as you would the Reserved BIOS Boot Area partition- create it first on either/any drive in the would-be RAID array, just don't create it on any of the other drives. When the time comes to create the swap and ext4 (or whatever floats your boat), each drive will lose however much space the ESP occupies on that first drive, so in my case I lost 500MB per drive- since RAID partitions must be the same size, if I take 500MB away from / to use for the ESP, I reduce the size of that partition by 500MB, which means that partition's counterparts on other drives also lose 500MB, only difference being the 500MB on the other drives isn't used for anything since the ESP is only on that first drive. I only have one other drive, so that's not bad.

EDIT: This applies to RAID0 and RAID1.

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