[DRBD-user] DRBD7/8 + kernel 2.6.22.1 + load + Primary power off = weird problem

[Lars Ellenberg]

On Fri, Jul 27, 2007 at 10:35:41AM +0300, Igor Anishchuk wrote:
> Hello Lars, others!
> 
> I've found the latest kernel release where everything works well.
> It is 2.6.21.6.

the default settings for vm.dirty_ratio and vm.dirty_background_ratio
have been cut down considerably in 2.6.22.  this should not have any
impact on drbd, at least not on drbd 8, also, we have deployments where
we hand-tuned to even less, and it is running fine.  but it is still
possible that you hit some vm deadlock.

to verify whether this would affect you,
have a look into /proc/sys/vm/dirty_ratio and
.../dirty_background_ratio, defaults before 2.6.22 have been
40 and 10, now 10 and 5, respectively.

also, if you can setup sysrequest, and then trigger a task dump
of "hanging" processes when it "freezes",
might help to understand what is going on.

-- 
: Lars Ellenberg                            Tel +43-1-8178292-0  :
: LINBIT Information Technologies GmbH      Fax +43-1-8178292-82 :
: Vivenotgasse 48, A-1120 Vienna/Europe    http://www.linbit.com :
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