Not exactly true, although it may still apply to fdisk or gdisk.

I had not tried that before, but I suspected gparted could handle that since it uses libparted-dmraid to handle md devices. As a test I just created a raid5 array (/dev/md0) using mdadm, then used gparted to create a partition table, define 3 partitions, and format all as ext4 on that array. The partitions were named /dev/md0p1, /dev/md0p2, & /dev/md0p3.

The device can also be directly defined as a PV using pvcreate then added to a VG in an LVM system. It then is seen by gparted as an LVM partition. I have done this on several different systems.

NP.
I did not anticipate you going back to disks after the partitioning was done with gparted, but since it worked that was a great trade-off over doing it manually.
Apparently after the partition table was created then disks was able to handle the raid device the same as any other disk. It now did not have to deal with the underlying hardware/raid device, but only with the partitioning & formatting (already done) & mounting while defining a mount point.
We learn something new every day!!

And we do not mind hanging with someone who has a problem. Helping and learning are the reasons we are here in the first place! ;-)

created a raid5 array (/dev/md0) using mdadm, then used gparted to create a partition table, define 3 partitions,
That is exactly how I started messing with RAID.
Of course some though it was nuts to have RAID5 on SAME disk!
That original scheme is still around and some day I'll get ambitious and use what is now scattered among 7 (!) USB and SATA disks. (If I can find it .... I am counting on grep... )

computersavvy, Thanks for the clarification.

That is nuts, but for learning it is OK. It just totally defeats the hardware redundancy that is built into the design of raid5, so don't rely on it to use for long periods.

Why? What file system do you put on top of mdadm? I was looking at btrfs raid 10.