Re: change UUID of RAID devcies

[Reindl Harald <h.reindl@thelounge.net>]

Am 12.09.22 um 23:37 schrieb Wol:
> On 12/09/2022 16:04, Reindl Harald wrote:
>> the reason for that game is that the machines are running for 10 years 
>> now and all the new desktop hardware can't hold 4x3.5" disks and so 
>> just put them in a new one isn't possible
> 
> How many SATA ports does the mobo have? Can you --replace onto the new 
> drives (especially if it's raid-10!), then just fail the remaining two 
> drives?
> 
> Iirc raid-10 doesn't require the drives to be the same size, so provided 
> the two new drives are big enough, that should just work.
> 
> Then with just two drives you change the raid to raid-1

i had this idea also and the drives have 3 partitions in that order, two 
machines 4x1TB and two machines 4x2TB

/boot is a RAID1, the other two RAIDS are RAID10

/dev/md0       ext4  482M     77M  401M   17% /boot
/dev/md1       ext4   29G    8,9G   20G   31% /
/dev/md2       ext4  3,6T    2,0T  1,7T   55% /data

/dev/md0       ext4  474M     45M  426M   10% /boot
/dev/md1       ext4   39G     22G   17G   58% /
/dev/md2       ext4  1,8T    1,1T  699G   61% /data

when i understand you correctly:

* replace two disks with double sized SSD's
* partition / and /data double sized
* "mdadm /dev/md1 --add /dev/sdcX" the double sized
* wait resync
* finally remove the two old half sized
* reshape md1 and md2 to RAID1

how would the command look for "Then with just two drives you change the 
raid to raid-1"?

----------

BTW: currently the machines are BIOS-boot - am i right that the 2 TB 
limitation only requires that the parts which are needed for booting are 
on the first 2 TB and i can use 4 TB SSD's on the two bigger machines?

in that case i think i would need GPT partitioning and does GRUB2 
support booting from GPT-partitioned disks in BIOS-mode?