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I'm running a file server using Linux software raid, set up as raid6. As filesystem I've chosen btrfs. However, I'm not using btrfs own raid6 implementation as it's not very stable yet. So basically, I'm using raid on the block level of things. Additionally, I'm making backups to another location of really important data. Lastly, I've connected a UPS to the server to protect against power loss and surges.

My questions:

  1. I'm aware raid6 gives quite a good protection against harddrive failure, but will btrfs on top of it really detect bit rot and correct it? If so, how is that possible without filesystem raid1?

  2. Do md go through the raid6 block from time to time to find and correct corruptions? Do I need to schedule it?

  3. If I've done things wrong, what do you recommend I do instead, if I want good protection against data failure and bit rot?

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2 Answers 2

up vote 3 down vote accepted

1: In your configuration, btrfs should detect data corruption but won't correct it as there is no data redundancy as far as btrfs is concerned.

2: RAID6 doesn't detect nor reliably protect against bit corruption. It only protects against disk failure and in some cases might detect unused still bad blocks.

3: If btrfs RAID6 is not ready, you might consider either btrfs mirroring or ZFS RAIDZ2.

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(Answering a question that disappeared: will RAIDZ6 protect against bit-rot) Yes, it does it by design. There is still a risk of corruption due to RAM bit-flip. End-to-end data integrity requires ECC RAM and is recommended at least for production systems. By the way, that's RAIDZ2, not RAIDZ6. –  jlliagre Jun 16 '14 at 20:13

In your setup it would not.

What I would recommend is using ZFS built-in RAID-z2, which is then able to perform bit-rot recovery. Enabling lz4 compression will also provide better performance, as well as space savings.

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