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Forum Discussion
Checksum capabilities with btrfs on top of mdraid?
As I understand, readynas OS6 implements btrfs on top of an mdraid volume because native raid-support in btrfs is still a bit experimental (introduced 2013). How does this affect the checksum capabili...
btrfs checksums apply to metadata and data blocks. OS6 lets you turn them off if you like. They are crc32 checksums - and therefore in themselves are only useful for error detection, not recovery.
Classic RAID protection only kicks in when sectors cannot be read. Then redundancy is used to reconstruct them. Re-writing the data blocks at that point should result in reallocated sectors (which then can be read, at least for a while). So I don't think your scenario in (3) will be corrected. btrfs itself can store redundant metadata, so that is perhaps an exception.
btrfs snapshots are more useful than anything you can get in ext4, and there is no need for journalling. It also does not have the RAID expansion limits that ext4 implementations in the 4.2.x NAS have.
Personally I have found btrfs in OS6 to be stable, and I do like the snapshot feature. But I am also perfectly fine with ext4+journalling, and have no immediate plans to install OS6 on my pro-6.
I don't know what plans Netgear has in the future. Integrating a variant of RAID into the filesystem (which is basically what btrfs is doing) is a good idea in principle. You'd need a factory reset to migrate to that though, and obviously it will need a lot of testing. Keeping RAID as a strictly separate lower layer is definitely less complex.
Classic RAID protection only kicks in when sectors cannot be read. Then redundancy is used to reconstruct them. Re-writing the data blocks at that point should result in reallocated sectors (which then can be read, at least for a while). So I don't think your scenario in (3) will be corrected. btrfs itself can store redundant metadata, so that is perhaps an exception.
btrfs snapshots are more useful than anything you can get in ext4, and there is no need for journalling. It also does not have the RAID expansion limits that ext4 implementations in the 4.2.x NAS have.
Personally I have found btrfs in OS6 to be stable, and I do like the snapshot feature. But I am also perfectly fine with ext4+journalling, and have no immediate plans to install OS6 on my pro-6.
I don't know what plans Netgear has in the future. Integrating a variant of RAID into the filesystem (which is basically what btrfs is doing) is a good idea in principle. You'd need a factory reset to migrate to that though, and obviously it will need a lot of testing. Keeping RAID as a strictly separate lower layer is definitely less complex.
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