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From: Zdenek Kabelac <zkabelac@redhat.com>
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Date: Mon, 13 Nov 2017 16:20:16 +0100
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Subject: Re: [linux-lvm] LVM hangs
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To: LVM general discussion and development <linux-lvm@redhat.com>, Alexander 'Leo' Bergolth <leo@strike.wu.ac.at>

Dne 13.11.2017 v 16:12 Alexander 'Leo' Bergolth napsal(a):
> Hi!
> 
> On 11/13/2017 03:51 PM, Zdenek Kabelac wrote:
>> Dne 13.11.2017 v 14:41 Alexander 'Leo' Bergolth napsal(a):
>>> I have a EL7 desktop box with two sata harddisks and two ssds in a
>>> LVM raid1 - thin pool - cache configuration. (Just migrated to this
>>> setup a few weeks ago.)
>>>
>>> After some days, individual processes start to block in disk wait.
>>> I don't know if the problem resides in the cache-, thin- or raid1-layer
>>> but the underlying block-devices are fully responsive.
>>>
>>> I have prepared some info at:
>>>  �� http://leo.kloburg.at/tmp/lvm-blocks/
>>>
>>> Do the stack backtraces provide enough information to locate the source
>>> of the blocks?
>>>
>>> I'd be happy to provide additional info, if necessary.
>>> Meanwhile I'll disable the LVM cache layer to eliminate this potential
>>> candidate.
>>
>> It would be probably nice to see the result of 'dmsetup status'
> 
> 
> OK. Will be included next time.
> 
> 
>> I'd have guessed you are probably hitting� 'frozen' raid state
>> which is unfortunate existing upstream bug.
> 
> Are you talking about RH bug 1388632?
> https://bugzilla.redhat.com/show_bug.cgi?id=1388632
> 
> Unfortunately I can only view the google-cached version of the bugzilla
> page, since the bug is restricted to internal view only.
> 

that could be similar issue yes

> But the google-cached version suggests that the bug is mainly hit when
> removing the raid-backed cache pool under IO.
> 
> I my scenario, no modification (like cache removal) of the lvm setup was
> done when the blocks occured.

Easiest is to check  'dmsetup status' - just to exclude if it's frozen raid case.


Zdenek