I have a Ubuntu server with the operating system installed on a raid1 created with two 500GB devices. the second drive failed. I now how to replace it, but my goal now is to move the operating system on a 4 Gb USB drive (as the whole server installation is 1.5 Gb). Maybe it looks like a crazy thing but I'm confident that a raid created with two USB drive can be more efficient in my scenario. This is not a critical server, used for testing purpose, but the goal is not to reinstall it from zero and use the OS as it is now in the 500gb device that still exists. Any idea how to do that?
migrated from stackoverflow.com Oct 6 '14 at 13:46
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No, for the second spot it is not a bad idea, although this question had probably a better place on serverfault.com .
The usb disks are for the linux practically disks on /dev/sd?, just as any other. Probably you will have some problems with the bios bioting, and there will be a problem that after every disk failure (in case of the usb it will happen much often) there will be a full raid resync.
Anyways, your goal has practically 4 steps:
Only the first step has with mdadm anything to do. You can create a raid mirror from two usb pendrives just as you did it from two disks:
Probably you will have a lot other questions during the 3 other steps. This site, and the serverfaulr SE are waiting you with them.