On Fri, Aug 14, 2015 at 12:12 PM, Timothy Normand Miller <theo...@gmail.com> wrote: > Sorry about that empty email. I hit a wrong key, and gmail decided to send. > > Anyhow, my replacement drive is going to arrive this evening, and I > need to know how to add it to my btrfs array. Here's the situation: > > - I had a drive fail, so I removed it and mounted degraded. > - I hooked up a replacement drive, did an "add" on that one, and did a > "delete missing". > - During the rebalance, the replacement drive failed, there were OOPSes, etc. > - Now, although all of my data is there, I can't mount degraded, > because btrfs is complaining that too many devices are missing (3 are > there, but it sees 2 missing).
It might be related to this (long) bug: https://bugzilla.kernel.org/show_bug.cgi?id=92641 While Btrfs RAID 1 can tolerate only a single device failure, what you have is an in-progress rebuild of a missing device. If it becomes missing, the volume should be no worse off than it was before. But Btrfs doesn't see it this way, instead is sees this as two separate missing devices and now too many devices missing and it refuses to proceed. And there's no mechanism to remove missing devices unless you can mount rw. So it's stuck. > So I could use some help with cleaning up this mess. All the data is > there, so I need to know how to either force it to mount degraded, or > add and remove devices offline. Where do I begin? You can try to ask on IRC. I have no ideas for this scenario, I've tried and failed. My case was throw away, what should still be possible is using btrfs restore. > Also, doesn't it seem a bit arbitrary that there are "too many > missing," when all of the data is there? If I understand correctly, > all four drives in my RAID1 should all have copies of the metadata, No that's not correct. RAID 1 means 2 copies of metadata. In a 4 device RAID 1 that's still only 2 copies. It is not n-way RAID 1. But that doesn't matter here, the problem is that Btrfs has a narrow idea of the volume, it assumes without context that once the number of devices is below the minimum, the volume can't be mounted. In reality, an exception exists if the failure is for an in-progress rebuild of a missing drive. That drive failing should mean the volume is no worse off than before but Btrfs doesn't know that. Pretty sure about that anyway. > and of the remaining three good drives, there should be one or two > copies of every data block. So it's all there, but btrfs has decided, > based on the NUMBER of missing devices, that it won't mount. > Shouldn't it refuse to mount if it knows there is data missing? For > that matter, why should it even refuse in that case? So some data > might missing, so it should throw some errors if you try to access > that missing data. Right? I think no data is missing, no metadata is missing, and Btrfs is confused and stuck in this case. -- Chris Murphy -- 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
