Re: btrfs-replace OOM on 2GB machine

[Georg Lukas <georg@op-co.de>]

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* Austin S Hemmelgarn <ahferroin7@gmail.com> [2015-11-17 13:56]:
> While it probably isn't related to the OOM issue, I would be particularly
> wary of using BTRFS on SMR disks, we've had multiple reports of serious
> issues with them (and IIRC, they were all the same model of 8TB Seagate SMR
> disks).

Yes, that's exactly the model I have here, but the problems are related
to the SMR support in the kernel, and hopefully not at all to btrfs.
With the latest patch by Martin K. Petersen [*], the disks seem to be
stable and reliable, finally.

[*] https://bugzilla.kernel.org/show_bug.cgi?id=93581

> Hmm, it looks like things weren't all RAID1, you've got a little over 1TiB
> of data that was RAID0, and that may be why you can't rebuild the FS.  This
> shouldn't be causing an OOM condition, but it definitely means things are
> not fully recoverable.

I think this was caused by my attempt to rebalance the degraded RAID1
into RAID0, and there are indeed some files on the fs that I can't read
any more. As this is not a production system, I'm not very bothered - I
just wanted to find out if I can get it back to live, which currently
fails on the replace.

> This actually looks like it's a different issue potentially, for some reason
> BTRFS is trying to scrub the missing disk (which won't work of course).

Indeed, scrubbing the degraded disk set did not succeed either.

If you need me to perform any other actions on that disk set, let me
know on- or off-list.

Georg
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