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From: Graham Fleming <graham.fleming@gmail.com>
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Subject: RE: Scrubbing with BTRFS Raid 5
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Date: Tue, 21 Jan 2014 01:06:37 -0800
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Thanks for all the info guys.

I ran some tests on the latest 3.12.8 kernel. I set up 3 1GB files and attached them to /dev/loop{1..3} and created a BTRFS RAID 5 volume with them.

I copied some data (from dev/urandom) into two test files and got their MD5 sums and saved them to a text file.

I then unmounted the volume, trashed Disk3 and created a new Disk4 file, attached to /dev/loop4.

I mounted the BTRFS RAID 5 volume degraded and the md5 sums were fine. I added /dev/loop4 to the volume and then deleted the missing device and it rebalanced. I had data spread out on all three devices now. MD5 sums unchanged on test files.

This, to me, implies BTRFS RAID 5 is working quite well and I can in fact, replace a dead drive.

Am I missing something?