Re: Kernel 3.19 and still "disk full" even though 'btrfs fi df" reports enough room left?

[Austin S Hemmelgarn <ahferroin7@gmail.com>]

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On 2015-11-19 13:28, Hugo Mills wrote:
> On Thu, Nov 19, 2015 at 06:35:24PM +0100, linux-btrfs.tebulin@xoxy.net wrote:
>> Will newer kernels do the balance on their own?
>
>     I think it's on the "projects" list on the wiki, so it may get done
> eventually. As I said above, I'm not aware of anyone working on it.
TBH, while it would be a nice feature, it's also something that has the 
potential to cause issues for people if it all happens at once.  IN many 
of the cases I've seen, the usual issue is lots of mostly empty data 
chunks (usually less than 20% in the two times I've run into this 
myself).  Based on this, having something in the kernel that could scan 
chunk usage every now and then, and repack mostly empty chunks if there 
is space already allocated in existing chunks, would probably 
significantly reduce the chances of this happening for most people, and 
cause much less noticeable performance degradation than triggering a 
full balance on a chunk allocation failure.  Since I started using a 
cron job to do a daily balance of chunks less than 20% full, and a 
weekly one for chunks less than 50% full, I've not run into these issues 
at all, and actually see on average better performance on my tradition 
hard disks.



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