@Noggin Hello again.
Re:
I don’t see why not. Assuming the the devices are compatible, ie size etc. It may be that you would need to edit the grub config and fstab if device names were different, but nothing that is not required for any other linux install undergoing this 'transition". And given both systems are likely to be ‘compatible’ ie both USB boot devices, this method should be good.
Only caveat I can think of is that during the copy process, or more exactly at the end of it, you don’t want to to mount both volumes, or to be safe, do any btrfs stuff while both instances of what is effectively the same pool are simultaneously connected to the same machine. Btrfs uses pool id to identify pool members and after the clone you will have 2 pools with identical uuid. So just don’t do btrfs stuff with both of them simultaneously connected as that would be bad. I think this has been addressed in much later kernels than we use in our CentOS variants but is a definite concern for our current CentOS offerings.
That’s a tricky question, and one I would like a clear answer to also. I used to recommend the SanDisk Extreme USB 3.0 32 GB and up as they have working S.M.A.R.T and are essentially a USB-to-SATA controller bridge with SSD attached and are super fast on read and write. But they have been discontinued and replaced with the “Pro” USB 3.1 variant (I have a 64 GB version) where there is, as yet, no working S.M.A.R.T. The newer Pro variant is faster on write but slower on read I think.
Which USB drive are you referencing in the following?
USB key performance came up recently and I posted a few basic speed tests. See the following forum post for these.
Incidentally, did you know that Rockstor supports custom smartctl options such as you have used in your post:
And the “-d scsi”, as well as “-d sat”, are supported. See the doc subsection: Disk Custom S.M.A.R.T Options
Hope that helps.