On Wed, Apr 22, 2020 at 12:55:08PM +0200, Stefanie Leisestreichler wrote: > > > On 22.04.20 12:44, Hugo Mills wrote: > > You can't set up btrfs RAID-1 to use only one device. It's only > > possible to end up like that if you set up a 2-device RAID-1 and then > > unplug a device and mount it in degraded mode. > > It was this sentence in the btrfs wiki, what confused me, also comments in > the net that btrfs is not giving you RAID with redundant data > (https://btrfs.wiki.kernel.org/index.php/FAQ): > > "It is possible with all of the descriptions below, to construct a RAID-1 > array from two or more devices, and have those devices live on the same > physical drive. This configuration does not offer any form of redundancy for > your data." There's a difference between "device" and "disk" here. If you make two partitions on one device, and that device fails, then there's no (disk) redundancy. If you make two partitions on one disk and one partition on another disk, and use all three partitions (block devices) to make a RAID-1, then you're still going to lose the filesystem if the disk with two partitions on it fails. I'm not sure what the comments are about not giving redundant data -- if you configure your FS to use one of the redundant RAID levels, then that's what you get. Hugo. -- Hugo Mills | emacs: Eighty Megabytes And Constantly Swapping. hugo@... carfax.org.uk | http://carfax.org.uk/ | PGP: E2AB1DE4 |
