Re: [linux-lvm] LVM hangs

["Alexander 'Leo' Bergolth" <leo@strike.wu.ac.at>]

On 2017-11-16 12:47, Zdenek Kabelac wrote:
> Dne 16.11.2017 v 12:02 Alexander 'Leo' Bergolth napsal(a):
>> On 2017-11-13 15:51, 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.
> 
> From the plain look over those file - it doesn't even seem there is
> anything wrong with dm devices as such.
> 
> So it looks like  possibly XFS got into some unhappy moment.
>
> I'd probably recommend to open regular  Bugzilla case  and attach files
> from your directory.

OK.

> You can try if individual devices in the  'stack' are blocked.
> i.e. try 'dd' read from every 'dm'  if there is something blocked.

No device is currently blocking. I can read from all LV devices
(including meta devices), all underlying PVs and all filesystems:

for dev in $(lvs -a -olv_dm_path --noheadings); do
  echo $dev;
  dd if=$dev of=/dev/null bs=4k count=10000 iflag=direct;
done
for pv in $(pvs -oname --noheadings); do
  echo $pv
  dd if=$pv of=/dev/null bs=4k count=10000 iflag=direct
done
echo 3 >/proc/sys/vm/drop_caches
for mp in $(findmnt -t xfs,ext4 -o TARGET -l -n); do
  echo $mp;
  tar -cf- --one-file-system "$mp" 2>/dev/null| head -c $((1024**3))
>/dev/null;
done

> From status all device looks fully operational and also process stack
> trace do look reasonable idle.
> 
> I'm not sure how 'afs' is involved here - can you reproduce without afs ?

OK. I'll try.

Thanks for your help!

--leo
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