On Mon, Oct 12, 2015 at 07:43:50AM +1300, Warren Hughes wrote: > Hi guys, just added a new Seagate Archive 8TB drive to my BTRFS volume > and I'm getting a tonne of errors when balancing or scrubbing. > > A short smartctl test reports fine, running a long one now. Will also > run seatools from a bootable DOS USB while at work today. > > Running latest firmware on my 9240-8i which explicitly supports this drive. > > I'm finding it very hard to tell if SMR drives are OK with BTRFS > currently - anyone chime in?
I assume you have the host-managed SMR drives. This type needs tweaks to the operating system so the write patterns play well with the SMR constraints. Btrfs does not support that out of the box, but my colleague Hannes Reinecke managed to get it working with some minor changes to the allocator and disabled writing of superblock copies. For full support of SMR we'd have to change more than that, currently nothing prevents to write "backwards" in a given chunk that is allowed to be written only in the append way. So you can get mixed results when trying to use the SMR devices but I'd say it will mostly not work. But, btrfs has all the fundamental features in place, we'd have to make adjustments to follow the SMR constraints: * we can map the blockgroups to the SMR chunks (in some multiples) * remember the write pointers and do only append writes (easy with COW) * if the chunk is getting full, mark it read-only, rebalance the live data somewhere else and reset the chunk and the pointer I have some notes at https://github.com/kdave/drafts/blob/master/btrfs/smr-mode.txt -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
