[libvirt-users] Ang: Re: Ang: Re: attaching storage pool error

[Yuan Dan]

----- Original Message -----
> 
> Hi and thanks for your important input,Dan!
> 
> 
> > > 
> > > 
> > > System centos7, system default libvirt version.
> > > 
> > > I've succeeded to create an npiv storage pool, which I could start
> > > without
> > > problems. Though I couldn't attach it to the vm, it throwed errors when
> > > trying. I want to boot from it, so I need it working from start. I read
> > > one
> > > of Daniel Berrange's old(2010) blogs about attaching an iScsi pool, and
> > > draw
> > > my conclusions from that. Other documentation I haven't found. Someone
> > > can
> > > point me to a more recent documentation of this?
> > > 
> > > Are there other mailing list in the libvirt/KVM communities that are more
> > > focused on storage? I'd like to know about these, if so, since I'm a
> > > storage
> > > guy, and fiddle around a lot with these things...
> > > 
> > > There are quite a few things I'd like to know about, that I doubt this
> > > list
> > > cares about, or have knowledge about, like multipath devices/pools,
> > > virtio-scsi in combination with npiv-storagepool, etc.
> > > 
> > > So anyone that can point me further....?
> > 
> > http://libvirt.org/formatstorage.html
> > https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Virtualization_Deployment_and_Administration_Guide/sect-NPIV_storage.html
> > 
> > Hope it can help you to get start with it.
> > 
> > 
> > Unfortunatly I have already gone through these documents, several times as
> > well, but these are only about the creation of storage pools, not how you
> > attach them to the guest.
> 
> If the pool is ready, here are kinds of examples
> http://libvirt.org/formatdomain.html#elementsDisks
> 
> you can use it in guest like this:
>     <disk type='volume' device='disk'>
>       <driver name='qemu' type='raw'/>
>       <source pool='iscsi-pool' volume='unit:0:0:1' mode='host'/>
>       <auth username='myuser'>
>         <secret type='iscsi' usage='libvirtiscsi'/>
>       </auth>
>       <target dev='vdb' bus='virtio'/>
>     </disk>
> 
> 
> 
> 
> 
> 
> 
> As I described above, I created an npiv pool for my FC backend. I'd also like
> to get scsi pass through, which seems to be possible only if I use
> "device=lun". Can I NOT use "device=lun", and then obviously NOT get "scsi
> pass through", if I use an npiv storage pool? Is the only way to get "scsi
> pass through" to NOT use a storage pool, but instead use the host lun's?
> 
> 
> What do you think about this?:
> 
> <disk type='volume' device='disk'>
>   <driver name='qemu' type='raw'/>
>   <source pool='vhbapool_host8' volume='unit:0:0:1'/>
>   <target dev='hda' bus='ide'/>
> </disk>
> 
> 
> But I'd prefer to be able to use something like this instead:
> 
> 
> 
> <disk type='volume' device='lun'>
>   <driver name='qemu' type='raw'/>
>   <source pool='vhbapool_host8' volume='unit:0:0:1'/>
>   <target dev='vda' bus='scsi'/>
> </disk>
> 
> But that might not be possible...?
> 

No need to prepare the pool for the following 2 usage.
Is it satisfied your requirement ?

http://libvirt.org/formatdomain.html#elementsHostDevSubsys

    <hostdev mode='subsystem' type='scsi'>
      <source>
        <adapter name='scsi_host0'/>
        <address bus='0' target='0' unit='0'/>
      </source>
      <readonly/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </hostdev>


  <disk type='block' device='disk'>
     <driver name='qemu' type='raw'/>
     <source dev='/dev/disk/by-path/pci-0000\:04\:00.1-fc-0x203400a0b85ad1d7-lun-0'/>
     <target dev='sda' bus='scsi'/>
  </disk>

> 
> 
> A couple of additional questions here:
> 
> * Since the target device is already defined in the pool, I don't see the
> reason for defining it here as well, like in your example with the iscsi
> pool?
> * I'd like to use virtio-scsi combined with the pool, is that possible?
> * If so, how do I define that? I understand I can define a controller
> separatly, but how do I tell the guest to use that specific controller in
> combination with that pool?

    <disk type='volume' device='lun'>
      ... 
      <source pool='poolname' volume='unit:0:0:1'/>
      <target dev='sda' bus='scsi'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>
    <controller type='scsi' index='0' model='virtio-scsi'>
    </controller>

> * Since the npiv pool obviously is a pool based on an fc initiator, the fc
> target can/will provision more lun's to that initiator, how will that effect
> the pool and the guest's access to new lun's? In this example the volume
> says 'unit:0:0:1', and I guess that will change if there will be more lun's
> in there? Or is that "volume unit" the "scsi target device", and can hold
> multiple lun's?


<source> is not a zeroOrMore sub-element of <disk>.

If a new lun added, then you should see a new vol in the pool,
by adding a new <disk> with the new vol, the guest can access the new lun.

The value for the volume attribute will be the output from the 
"Name" column of a "virsh vol-list [pool-name]" command. 



Thanks
Dan

> 
> 
> Regards Johan
> 
> > 
> > > 
> > > Rgrds Johan
> > > 
> > > 
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