Resending as previous comments did not need any changes. Currently BTRFS allows you to make bad choices of data and metadata levels. For example -d raid1 -m raid0 means you can only use half your total disk space, but will loose everything if 1 disk fails. It should give a warning in these cases.
This patch is a follow up to [PATCH v2] btrfs-progs: check metadata redundancy in order to cover the case of using balance to convert to such a set of raid levels. A simple example to hit this is to create a single device fs, which will default to single:dup, then to add a second device and attempt to convert to raid1 with the command btrfs balance start -dconvert=raid1 /mnt this will result in a filesystem with raid1:dup, which will not survive the loss of one drive. I personally don't see why the tools should allow this, but in the previous thread a warning was considered sufficient. Changes in v2 Use btrfs_get_num_tolerated_disk_barrier_failures() Signed-off-by: Sam Tygier <samtyg...@yahoo.co.uk> From: Sam Tygier <samtyg...@yahoo.co.uk> Date: Sat, 3 Oct 2015 16:43:48 +0100 Subject: [PATCH] Btrfs: Check metadata redundancy on balance When converting a filesystem via balance check that metadata mode is at least as redundant as the data mode. For example give warning when: -dconvert=raid1 -mconvert=single --- fs/btrfs/volumes.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 6fc73586..40247e9 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -3584,6 +3584,12 @@ int btrfs_balance(struct btrfs_balance_control *bctl, } } while (read_seqretry(&fs_info->profiles_lock, seq)); + if (btrfs_get_num_tolerated_disk_barrier_failures(bctl->meta.target) < + btrfs_get_num_tolerated_disk_barrier_failures(bctl->data.target)) { + btrfs_info(fs_info, + "Warning: metatdata has lower redundancy than data\n"); + } + if (bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT) { fs_info->num_tolerated_disk_barrier_failures = min( btrfs_calc_num_tolerated_disk_barrier_failures(fs_info), -- 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html