On 2025-08-29, alain williams <[email protected]> wrote: > On Fri, Aug 29, 2025 at 02:02:43PM +0100, mick.crane wrote: > >> I have my data on a separate disk that I copy to various places every now >> and again. >> I guess simplest is original plan ( as have been previously given the >> incantation ) to get 3 ~200Gb disks and dd to them. > > If your purpose is backup - then you are *far* better mounting the disk as a > file system and then copying files somewhere using tar or cpio. That somewhere > could be a disk - although something like a USB memory stick would be better > as > these are more robust and smaller than a hard disk.
Yes. I don't understand what he is trying to achieve beyond using dd because it's cool or something. Maybe it is cool. My understanding is that it produces a byte for byte copy (my understanding without looking anything up). Now, I am fuzzy on a RAID array (the OP's question calls this to my mind), which I think is a series of disks with the same content so that if one fails, you can replace it with another. But not to be used as a backup strategy. > Why: > > • you are copying the data (your files), not all the other bytes on disk (that > are useless to you) > > • the tar/cpio archive will be readable on a greater number of systems than > just the ones that support the file system on your disk (prolly ext2/similar) >
