BTRFS: RAID-0 on drives of different size?

[BlueFusion]

Hey folks,

I've been having great success with using btrfs for the past few years. I've been running it on my old ASUS laptop on top of dm_crypt with no problem for over a year. I bought a replacement ASUS laptop 2 months ago and did the same thing. The AES-NI instruction helped, but overall the laptop is just much faster

With the success of btrfs as the root filesystem on my laptops now for some time with no hiccups, I feel confident that it is ready for use as the rootfs on my desktop which stores many TB of data. Everything that is important is backed up on a seperate drive and the REALLY important stuff is backed up to an offsite server.

This morning I decided to do away with ext4 across several disks and go with a dm_crypt btrfs array. I set it up as a JBOD array (-d single) for now.

I recently read (and I can not find where I read it) that btrfs will try to utilize space efficiently if different sized disks are used.

Lucky me, I have a 1000GB drive and 2x 500GB drives. Does anybody here know if btrfs in RAID-0 will store the data in a way that data on the 500GB drives are striped with the 1TB drive so 2TB of data can be stored (less the RAID-1 metadata)?
_________________
i7-940 2.93Ghz | ASUS P6T Deluxe (v.1) | 24GB Triple Channel RAM | nVidia GTX660
4x 4TB Seagate NAS HDD (Btrfs raid5) | 2x 120GB Samsung 850 EVO SSD (Btrfs raid1)

[Randy Andy]

Hi BlueFusion

[BlueFusion]

Thanks Andy,

I used my Google-fu yesterday and read some other articles from late 2013, early 2014 and they seemed to indicate that RAID-1 works in the way I explained, but RAID-0.....sort of but not quite. RAID-1 makes two copies of each bit of data and is smart enough to make maximum use of the space available. RAID-0, however, does not quite work in this way. Instead, it stripes the data between all available drives, as any normal RAID-0 would. This causes the last 500GB of the 1000GB drive to go mostly unused (metadata does occupy the space).

I decided that I would give it a test run with some loop devices. Sure enough, it performed as described above.

If there's a way to limit the maximum number of stripes to 2, then that should allow it to utilize all of the space, like RAID-1. I have scouring the internet and man pages for an option like this but I have not found one yet.
_________________
i7-940 2.93Ghz | ASUS P6T Deluxe (v.1) | 24GB Triple Channel RAM | nVidia GTX660
4x 4TB Seagate NAS HDD (Btrfs raid5) | 2x 120GB Samsung 850 EVO SSD (Btrfs raid1)