28.04.2019 22:35, Hendrik Friedel пишет: > Hello, > > I intend to move to BTRFS and of course I have some data already. > I currently have several single 4TB drives and I would like to move the > Data onto new drives (2*8TB). I need no raid, as I prefer a backup. > Nevertheless, having raid nice for availability. So why not in the end. > I currently use ~6TB, so it may work, but I would be able to remove the > redundancy later. > > So, if I understand correctly, today I want > -m raid1 -d raid1 > > whereas later, I want > -m raid1 -d single > > What is very important to me is, that with one failing drive, I have no > risk of losing the whole filesystem, but only losing the affected drive. > Is that possible with both of these variants? >
With "single" data profile you won't lose filesystem, but you will irretrievably lose any data on the missing drive. Also "single" profile does not support auto-healing (repairing of bad copy from good copy). If this is acceptable to you, then yes, both variants will do what you want. > Is it possible to move between the two (doing a balance, of course? Yes as long as you have sufficient free space for target profile. > Any other thoughts/recommendations? > As of today there is no provision for automatic mounting of incomplete multi-device btrfs in degraded mode. Actually, with systemd it is flat impossible to mount incomplete btrfs because standard framework only proceeds to mount it after all devices have been seen. As long as you do not use systemd in initramfs you may be able to boot by passing suitable root mount flags on kernel command line.
