Le 09/08/2022 à 16:50, David T-G a écrit :
I have an existing 128G SSD.
Disk /dev/sda: 122104MiB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: pmbr_boot
Number Start End Size File system Name Flags
0.02MiB 1.00MiB 0.98MiB Free Space
1 1.00MiB 33793MiB 33792MiB linux-swap(v1) diskfarm-swap swap
2 33793MiB 66561MiB 32768MiB xfs diskfarmsuse
3 66561MiB 99329MiB 32768MiB diskfarmknop legacy_boot
4 99329MiB 122104MiB 22775MiB xfs diskfarm-ssd
I have obtained a shiny new 256G SSD to use as a mirror.
My final-view plan is, in
fact, to replace the 128 with another 256 and grow the -ssd data partition.
For a typical mirror-an-existing, I think that I need to create all of my
slices and the [degraded] mirror on the new, copy over the old, boot from new,
and then treat old as just another disk to shove in. There's the question of
making partitions larger for the RAID superblock info
If you choose to copy existing block device content (with dd or the
like) into a RAID array, then the RAID array device size must be at
least the same this, which implies that the RAID member devices is
sligthly bigger to take the RAID superblock into account.
If you choose to copy filesystem content (with cp, rsync or the like)
into a new filesystem, then you only need the RAID array device to be
big enough to fit the content.
As you can see, I have no free space on the little guy.
Actually no, we cannot see. We can only see that there is no free space
outside the partitions. But we cannot see if there is any free space
inside the partitions.
what do I do with the old guy?
Do whatever you like with the old drive except using it in the RAID
array. Why bother doing this and having to resize the RAID array when
you add the 2nd new drive ? Resizing a RAID array is a pain in the ass.
Just build the RAID array on the 2 new drives from the start.
if I'm essentially starting from scratch, should I
mirror the entire [yes, identical] drive and partition the metadevice,
*BSD-style, or mirror individual partitions?
IMO a single RAID array is simpler. If your distribution supports it,
you can either partition it with a partition table or use it as a LVM
physical volume and create logical volumes.
However I do not think it is possible to cleanly boot from an
unpartitioned drive used as a software RAID member, as a RAID capable
boot loader could hardly fit in the 4-KiB area before the RAID
superblock. So you still have to create a partition table on the raw
drives. Also, if you use GPT format and GRUB boot loader, you need to
create a small (100 kB to 1 MB) partition with type "BIOS boot" (or
libparted bios_grub flag).
