Am 12.09.22 um 23:37 schrieb Wol:

On 12/09/2022 16:04, Reindl Harald wrote:

quoted

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"?

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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?