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Right,

I agree that the dirty size of the cache could be the issue 
(particularly with SATA drives in a JBOD array without the help of any 
writeback caches etc).

You might even want to wind those settings down a bit more (3 and 6 
perhaps which means with 32G of ram your dirty cache size is between 1 
and 2G), should stop the massive IO stall.

regards

Mark


On 09/11/15 23:39, Heiko Krämer wrote:
>
> Hi Mark,
>
> nothing can be logged because all disks are stale.
> I see only an output on the IPMI
>
> blocked for more than 120 seconds
> kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
> this message.
>
> I found there could be a problem with the write caching of the disks.
> So i have reduced the available dirty cache:
>
> vm.dirty_background_ratio = 5
> vm.dirty_ratio = 10
>
>
> I hope this will solve the issue.
>
> You're right only a hard reboot can solve the problem because SSH
> login or other commands can't be executed because the whole system was
> frozen.
> That's the problem i can't get any deeper informations was happened.
>
>