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Btrfs comes to a crashing stop

November 15, 2016 — BarryK
I posted about btrfs yesterday:

I was getting quite excited about subvolumes and snapshots, could see enormous potential.

I created a USB stick with Quirky 8.x x86_64, the second partition has btrfs and a subvolume named "@" with the Quirky files. Yep, it boots.

The second partition on the USB stick is 29GB, and I had less than 1GB of files to copy into the subvolume.

The 'cp' operation reported "no space left on device", so only part of Quirky got copied. Enough to bootup, but broken.

This problem is reported many times on the Internet, such as this guy who copied only 6GB into a 400GB partition and got the same "no space left on device" error:

...he had a very big file, which triggered the error, however, elsewhere there are heaps of reports of the out-of-space error when there is heaps of space, not just when copying large files.

There are some esoteric instructions that may be used to "fix" this problem, however, I just want something that works.

Pity. I am going to patch the kernel with zfs and try that.
Perhaps there is a good reason why Ubuntu and some other distros have chosen zfs.


Puppy forum member 'scsijon' sent me an email, to the effect that many years ago, in the very early alpha days of Btrfs, they determined that Btrfs only works with RAID systems, not with a single drive.

There are a lot of posts on the Internet from people using it on a single drive, and indeed that was the recommendation I had from someone, to use for Puppy, a few years ago.

In fact, the official documentation says you can use a single drive, in various places, such as here:
With grub and a single disk, you might not need an initramfs. Grub generates a root=UUID=… command line that the kernel should handle on its own. Some people have also used GPT and root=PARTUUID= specs instead

There are many references to single-disk usage, and I presume that also means RAID-less. Both zfs and btrfs are mentioned as suitable for a single drive here, with zfs given the edge:

Ha ha, this guy is commenting on the above post:

Tags: linux