Mirroring Concatenated Drives in Nested RAID

Hi
Is it possible to RAID mirror a concatenated set of drives? The goal is to have expandable, redundant storage. One side of the mirrored RAID would be 1 TB + 3 TB drives and the other side would be a single 4 TB drive. As I add to the concatenated drive RAID, I would add the same amount of storage to the other side in the mirrored RAID.
Does this work or is a mirrored RAID a fixed size that can never be expanded once it's created?
Thanks! - Cliff

As "greyday records" says, a concatenated set of disks can be a collection of any sized disks and you get to use all the space.  In days of old, this was useful if you had files larger than the size of a single disk.  These days, you can get disks that are generally speaking much larger any file you might want to store.  If you wanted to have a large number of files all on the same file system then concatenated might be useful.
A RAID0 requires equal sized disks, or as "greyday records"s says, the smallest disk in the set is the controlling factor for how much space is used on any of the other disks in the set.  Any disk in the set larger than the smallest disk will have unused space.
A concatenated set of disks is as fast as the disk the data is being written to.  A RAID0 disk set can be much faster as the data can be written in parallel to each stripe in the set.  High Performance computing has been using striped (RAID0) sets for years to get data into and out of the CPU as fast as possible.  RAID0 still has more practical uses.

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