Any comments on this observation? On Sat, Jul 16, 2016 at 2:25 AM, Nitesh Konkar < [email protected]> wrote:
> Link: http://wiki.libvirt.org/page/NPIV_in_libvirt > Topic: Virtual machine configuration change to use vHBA LUN > > There is a NPIV storage pool defined on two hosts and pool contains a > total of 8 volumes, allocated from a storage device. > > Source: > > # virsh vol-list poolvhba0 > Name Path > ------------------------------------------------------------------------------ > unit:0:0:0 /dev/disk/by-id/wwn-0x6005076802818bda3000000000000366 > unit:0:0:1 /dev/disk/by-id/wwn-0x6005076802818bda3000000000000367 > unit:0:0:2 /dev/disk/by-id/wwn-0x6005076802818bda3000000000000368 > unit:0:0:3 /dev/disk/by-id/wwn-0x6005076802818bda3000000000000369 > unit:0:0:4 /dev/disk/by-id/wwn-0x6005076802818bda300000000000036a > unit:0:0:5 /dev/disk/by-id/wwn-0x6005076802818bda3000000000000380 > unit:0:0:6 /dev/disk/by-id/wwn-0x6005076802818bda3000000000000381 > unit:0:0:7 /dev/disk/by-id/wwn-0x6005076802818bda3000000000000382 > -------------------------------------------------------------------- > Destination: > -------------------------------------------------------------------- > # virsh vol-list poolvhba0 > Name Path > ------------------------------------------------------------------------------ > unit:0:0:0 /dev/disk/by-id/wwn-0x6005076802818bda3000000000000380 > unit:0:0:1 /dev/disk/by-id/wwn-0x6005076802818bda3000000000000381 > unit:0:0:2 /dev/disk/by-id/wwn-0x6005076802818bda3000000000000382 > unit:0:0:3 /dev/disk/by-id/wwn-0x6005076802818bda3000000000000367 > unit:0:0:4 /dev/disk/by-id/wwn-0x6005076802818bda3000000000000368 > unit:0:0:5 /dev/disk/by-id/wwn-0x6005076802818bda3000000000000366 > unit:0:0:6 /dev/disk/by-id/wwn-0x6005076802818bda300000000000036a > unit:0:0:7 /dev/disk/by-id/wwn-0x6005076802818bda3000000000000369 > -------------------------------------------------------------------- > > As you can see in the above output,the same set of eight LUNs from the > storage server have been mapped, > but the order that the LUNs are probed on each host is different, resulting > in different unit names > on the two different hosts . > > If the the guest XMLs is referencing its storage by "unit" number then is > it safe to migrate such guests because the "unit number" is assigned by the > driver according to the specific way it probes the storage and hence when you > migrate > these guests , it results in different unit names on the destination hosts. > Thus the migrated guest gets mapped to the wrong LUNs and is given the wrong > disks. > The problem is that the LUN numbers on the destination host and source host > do not agree. > Example, LUN 0 on source_host, for example, may be LUN 5 on destination_host. > When the guest is given the wrong disk, it suffers a fatal I/O error. (This is > manifested as fatal I/O errors since the guest has no idea that its disks just > changed out under it.)The migration does not take into account that the unit > numbers do > match on on the source and destination sides. > > So, should libvirt make sure that the guest domains reference NPIV pool > volumes by their > globally-unique wwn instead of by "unit" numbers? > > The guest XML references its storage by "unit" number. > > Eg:- > <disk type='volume' device='lun'> > <driver name='qemu' type='raw' cache='none'/> > <source pool='poolvhba0' volume='unit:0:0:0'/> > <backingStore/> > <target dev='vdb' bus='virtio'/> > <alias name='virtio-disk1'/> > <address type='pci' domain='0x0000' bus='0x00' slot='0x05' > function='0x0'/> > </disk> > > I am planning to write a patch for it. Any comments on the above > observation/approach would be appreciated. > > Thanks, > > Nitesh. > >
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