[Users] SD Disk's Logical Volume not visible/activated on some nodes

[Nir Soffer]

Hi Zdenek, can you look into this strange incident?

When user creates a disk on one host (create a new lv), the lv is not seen
on another host in the cluster.

Calling multipath -r cause the new lv to appear on the other host.

Finally, lvs tell us that vg_mda_free is zero - maybe unrelated, but unusual.

----- Original Message -----
> From: "Boyan Tabakov" <blade at alslayer.net>
> To: "Nir Soffer" <nsoffer at redhat.com>
> Cc: users at ovirt.org
> Sent: Monday, March 3, 2014 9:51:05 AM
> Subject: Re: [Users] SD Disk's Logical Volume not visible/activated on some nodes
> >>>>>> Consequently, when creating/booting
> >>>>>> a VM with the said disk attached, the VM fails to start on host2,
> >>>>>> because host2 can't see the LV. Similarly, if the VM is started on
> >>>>>> host1, it fails to migrate to host2. Extract from host2 log is in the
> >>>>>> end. The LV in question is 6b35673e-7062-4716-a6c8-d5bf72fe3280.
> >>>>>>
> >>>>>> As far as I could track quickly the vdsm code, there is only call to
> >>>>>> lvs
> >>>>>> and not to lvscan or lvchange so the host2 LVM doesn't fully refresh.
> > 
> > lvs should see any change on the shared storage.
> > 
> >>>>>> The only workaround so far has been to restart VDSM on host2, which
> >>>>>> makes it refresh all LVM data properly.
> > 
> > When vdsm starts, it calls multipath -r, which ensure that we see all
> > physical volumes.
> > 
> >>>>>>
> >>>>>> When is host2 supposed to pick up any newly created LVs in the SD VG?
> >>>>>> Any suggestions where the problem might be?
> >>>>>
> >>>>> When you create a new lv on the shared storage, the new lv should be
> >>>>> visible on the other host. Lets start by verifying that you do see
> >>>>> the new lv after a disk was created.
> >>>>>
> >>>>> Try this:
> >>>>>
> >>>>> 1. Create a new disk, and check the disk uuid in the engine ui
> >>>>> 2. On another machine, run this command:
> >>>>>
> >>>>> lvs -o vg_name,lv_name,tags
> >>>>>
> >>>>> You can identify the new lv using tags, which should contain the new
> >>>>> disk
> >>>>> uuid.
> >>>>>
> >>>>> If you don't see the new lv from the other host, please provide
> >>>>> /var/log/messages
> >>>>> and /var/log/sanlock.log.
> >>>>
> >>>> Just tried that. The disk is not visible on the non-SPM node.
> >>>
> >>> This means that storage is not accessible from this host.
> >>
> >> Generally, the storage seems accessible ok. For example, if I restart
> >> the vdsmd, all volumes get picked up correctly (become visible in lvs
> >> output and VMs can be started with them).
> > 
> > Lests repeat this test, but now, if you do not see the new lv, please
> > run:
> > 
> >     multipath -r
> > 
> > And report the results.
> > 
> 
> Running multipath -r helped and the disk was properly picked up by the
> second host.
> 
> Is running multipath -r safe while host is not in maintenance mode?

It should be safe, vdsm uses in some cases.

> If yes, as a temporary workaround I can patch vdsmd to run multipath -r
> when e.g. monitoring the storage domain.

I suggested running multipath as debugging aid; normally this is not needed.

You should see lv on the shared storage without running multipath.

Zdenek, can you explain this?

> >> One warning that I keep seeing in vdsm logs on both nodes is this:
> >>
> >> Thread-1617881::WARNING::2014-02-24
> >> 16:57:50,627::sp::1553::Storage.StoragePool::(getInfo) VG
> >> 3307f6fa-dd58-43db-ab23-b1fb299006c7's metadata size exceeded
> >>  critical size: mdasize=134217728 mdafree=0
> > 
> > Can you share the output of the command bellow?
> > 
> >     lvs -o
> >     uuid,name,attr,size,free,extent_size,extent_count,free_count,tags,vg_mda_size,vg_mda_free,lv_count,pv_count,pv_name
> 
> Here's the output for both hosts.
> 
> host1:
> [root at host1 ~]# lvs -o
> uuid,name,attr,size,vg_free,vg_extent_size,vg_extent_count,vg_free_count,tags,vg_mda_size,vg_mda_free,lv_count,pv_count
>   LV UUID                                LV
>       Attr      LSize   VFree   Ext     #Ext  Free  LV Tags
> 
> VMdaSize  VMdaFree  #LV #PV
>   jGEpVm-oPW8-XyxI-l2yi-YF4X-qteQ-dm8SqL
> 3d362bf2-20f4-438d-9ba9-486bd2e8cedf -wi-ao---   2.00g 114.62g 128.00m
> 1596   917
> IU_0227da98-34b2-4b0c-b083-d42e7b760036,MD_5,PU_f4231952-76c5-4764-9c8b-ac73492ac465
>    128.00m        0   13   2

This looks wrong - your vg_mda_free is zero - as vdsm complains.

Zdenek, how can we debug this further?

Nir