Re: btrfs-transacti hammering the system

[Duncan <1i5t5.duncan@cox.net>]

Hans van Kranenburg posted on Fri, 01 Dec 2017 18:06:23 +0100 as
excerpted:

> On 12/01/2017 05:31 PM, Matt McKinnon wrote:
>> Sorry, I missed your in-line reply:
>> 
>> 
>>> 2) How big is this filesystem? What does your `btrfs fi df
>>> /mountpoint` say?
>>>
>> 
>> # btrfs fi df /export/
>> Data, single: total=30.45TiB, used=30.25TiB
>> System, DUP: total=32.00MiB, used=3.62MiB
>> Metadata, DUP: total=66.50GiB, used=65.08GiB
>> GlobalReserve, single: total=512.00MiB, used=53.69MiB
> 
> Multi-TiB filesystem, check. total/used ratio looks healthy.

Not so healthy, from here.  Data/metadata are healthy, yes,
but...

Any usage at all of global reserve is a red flag indicating that
something in the filesystem thinks, or thought when it resorted
to global reserve, that space is running out.

Global reserve usage doesn't really hint what the problem is,
but it's definitely a red flag that there /is/ a problem, and
it's easily overlooked, as it apparently was here.

It's likely indication of a bug, possibly one of the ones fixed
right around 4.12/4.13.  I'll let the devs and better experts take
it from there, but I'd certainly be worried until global reserve
drops to zero usage.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman