Talk:Using Btrfs with Multiple Devices

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Encrytion over multiple devices

I'm curious about using btrfs with encryption over multiple devices. What is the best way?

If i have a btrfs volume on an encrypted partition (using dm-crypt/luks), and i want to expand it to another physical drive, would i want to setup an encrypted volume on the second drive as well, or would the first volume's encryption apply to the 2.

In other words should i run "btrfs-vol -a /dev/mapper/encrypted-vol2 /media/foo" or would "btrfs-vol -a /dev/sdc1 /media/foo" work just as well to maintain the encryption applied to the first volume. Doing so with both volumes encrypted seems to lead to significant performance loss (as would be expected). (Evilgold 22:27, 6 September 2010 (UTC))

RAID from Drives of Differing Capacities

I've already described it here: Talk:Project_ideas

--Ddfitzy 23:54, 1 August 2010 (UTC)

The article says "When you have drives with differing sizes and want to use the full capacity of each drive, you have to use the single profile for the data blocks." As I understand it, this is only necessarily true for 2.x Linux kernels. Linux 3.0 included the quasi-round-robin chunk allocation patch, which should allow RAID1 and RAID0 to use the full space on some disk sets (ex: 1TB drive and 2 500GB drives, or a 2TB and a 1TB + 2 500GB drives).
Bobpaul 17:46, 24 April 2013 (UTC)

RAID Levels Explained

It seems that in the btrfs world, "raid0" means "striped on two devies" and "raid1" means "duplicated to 2 devices". So if you have -mraid1 -draid1 on a set of 4 n sized disks, you can still only loose 1 at a time and you'll be able to fit 2n bytes of data. Normally, a raid1 across 4 n byte disks would allow you to lose up to 3 drives and only provide n bytes of storage space.

Do I understand this correctly? This should be described in the documentation. Bobpaul 17:46, 24 April 2013 (UTC)

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