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Currently, /home claims 880G of a 1TB drive. Photos are eating this up quickly, so I want to add a 1TB drive I have lying around to the computer to expand /home. I figured I could use btrfs (I don't mind moving it all off somewhere and copying back) to get space from both devices into one partition.

But all the tutorials I've seen seem to assume you use full disks of the same size. Will btrfs be able to deal with one full device + one partition, of differing sizes? Will it be able to use the full disk space with the default metadata-mirrored/data-striped settings, or will it be as if I had 2x880G ?

(I don't plan on data-mirroring, I'm guessing that would give me less space than I had originally – got some 3TB backup drives instead that already run btrfs, I figure I could rely on checksumming to tell me if there's data corruption.)

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(You know, I just noticed that BTRFS = butter-face. ఠ_ఠ) – Synetech Dec 8 '13 at 23:21
up vote 2 down vote accepted

Actually, all scenarios are possible. You can add whole device or partition. Any combination is legal, mixes included (I've used them myself). Naturally, metadata is mirrored, so they will have to fit in all drives/partitions. You can also disable metadata mirroring if really want.

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Thanks, I tried this now, following…, and it worked :) My fstab now says /dev/sda1 /home btrfs defaults,noatime,compress=lzo,device=/dev/sda1,device=/dev/sdb7 0 3 – unhammer Dec 8 '13 at 20:33

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