How to rebuild and add disk to raid?

Question

System administration

There is soft raid1 2*2 TB screws. What would be the best way to add a 4 TB screw to it? There is an idea to make raid 0 from the first two to equalize the size of the device, and then build raid 1 on top of two screws in raid 0 and the remaining 4 TB hdd. Or create a level 5 raid?

Answer 1

Or maybe you should leave them as separate entities, and use the second screw for backups?
Or using LVM to saw off from the screw 2GB, and to start up the second 2GB on a backup?
There are many options.

Answer 2

switch to "iron" implementations of RAID

Answer 3

It seems that using ZFS/MDADM/LVM you can create a stripe (RAID0) from two 2TB disks, create a stripe from a 4TB disk, and merge these stripes into a mirror. The volume will be 4TB.
With the same success, you can create Raidz in ZFS (zpool create poolname raidz uuid1 uuid2 uuid3) from three disks, where a 4TB disk will be equalized to 2TB, but the total raid size will still be the same 4TB.
2TB * 3 - 2TB = 4TB
This is all higher if you need fault tolerance.

Answer 4

Why is this array needed at all? Combining RAID0 into another RAID1 on top is an initially losing idea - neither speed nor reliability, just a waste of time. It seems that you just want "all files in one folder", well, it can be done without RAID at all. If you need speed - dance on the volume, for sure, buying an SSD and backing it up on some of these screws will be the most profitable solution. If you need about 4TB of data for quick access, then at least buy 2 more of these screws, at least for RAID5, should not be a problem either.