raid0, raid1, raid5, what to choose?

Hello,

I'd appreciate your recommendation on this:

I have three hdd with 3TB each. I intend to use them as raid5 eventually. currently I use them like this:

# mount|grep sd
/dev/sda1 on /mnt/Datenplatte type ext4
/dev/sdb1 on /mnt/BTRFS/Video type btrfs
/dev/sdb1 on /mnt/BTRFS/rsnapshot type btrfs

#df -h

/dev/sda1       2,7T  1,3T  1,3T  51% /mnt/Datenplatte
/dev/sdb1       5,5T  5,4T   93G  99% /mnt/BTRFS/Video
/dev/sdb1       5,5T  5,4T   93G  99% /mnt/BTRFS/rsnapshot

Now, what surprises me, and here I lack memory- is that sdb appears twice.. I think, I created a raid1, but how can I find out?

#/usr/local/smarthome# ~/btrfs/btrfs-progs/btrfs fi show /dev/sdb1
Label: none uuid: 989306aa-d291-4752-8477-0baf94f8c42f
Total devices 2 FS bytes used 2.68TB
devid 2 size 2.73TB used 2.73TB path /dev/sdc1
devid 1 size 2.73TB used 2.73TB path /dev/sdb1

Now, I wanted to convert it to raid0, because I lack space and redundancy is not important for the Videos and the Backup, but this fails:
~/btrfs/btrfs-progs/btrfs fi balance start -dconvert=raid0 /mnt/BTRFS/
ERROR: error during balancing '/mnt/BTRFS/' - Inappropriate ioctl for device

dmesg does not help here.

Anyway: This gave me some time to think about this. In fact, as soon as raid5 is stable, I want to have all three as a raid5. Will this be possible with a balance command? If so: will this be possible as soon as raid5 is stable, or will I have to wait longer?

Quoted 12 lines · Hendrik Friedel

Hello,

I'd appreciate your recommendation on this:

I have three hdd with 3TB each. I intend to use them as raid5 eventually. currently I use them like this:

# mount|grep sd
/dev/sda1 on /mnt/Datenplatte type ext4
/dev/sdb1 on /mnt/BTRFS/Video type btrfs
/dev/sdb1 on /mnt/BTRFS/rsnapshot type btrfs

Quoted 7 lines

#df -h

/dev/sda1       2,7T  1,3T  1,3T  51% /mnt/Datenplatte
/dev/sdb1       5,5T  5,4T   93G  99% /mnt/BTRFS/Video
/dev/sdb1       5,5T  5,4T   93G  99% /mnt/BTRFS/rsnapshot

Now, what surprises me, and here I lack memory- is that sdb appears twice.. I think, I created a raid1, but how can I find out?

Appearing twice in that list is more an indication that you have
multiple subvolumes -- check the subvol= options in /etc/fstab

Quoted 11 lines

#/usr/local/smarthome# ~/btrfs/btrfs-progs/btrfs fi show /dev/sdb1
Label: none uuid: 989306aa-d291-4752-8477-0baf94f8c42f
Total devices 2 FS bytes used 2.68TB
devid 2 size 2.73TB used 2.73TB path /dev/sdc1
devid 1 size 2.73TB used 2.73TB path /dev/sdb1

Now, I wanted to convert it to raid0, because I lack space and redundancy is not important for the Videos and the Backup, but this fails:
~/btrfs/btrfs-progs/btrfs fi balance start -dconvert=raid0 /mnt/BTRFS/
ERROR: error during balancing '/mnt/BTRFS/' - Inappropriate ioctl for device

/mnt/BTRFS isn't a btrfs subvol, according to what you have listed
above. It's a subdirectory in /mnt which is contains two subdirs (Video and rsnapshot) which are used as mountpoints for subvolumes.

Try running the above command with /mnt/BTRFS/Video instead (or
rsnapshot -- it doesn't matter which).

Quoted 6 lines

dmesg does not help here.

Anyway: This gave me some time to think about this. In fact, as soon as raid5 is stable, I want to have all three as a raid5. Will this be possible with a balance command? If so: will this be possible as soon as raid5 is stable, or will I have to wait longer?

Yes, it's possible to convert to RAID-5 right now -- although the
code's not settled down into its final form quite yet. Note that RAID-5 over two devices won't give you any space benefits over RAID-1 over two devices. (Or any reliability benefits either).

Hugo.

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