[ovirt-users] iSCSI and multipath

[Maor Lipchuk]

Hi Nicolas,

Which DC level are you using?
iSCSI multipath should be supported only from DC with compatibility
version of 3.4

regards,
Maor

On 06/09/2014 01:06 PM, Nicolas Ecarnot wrote:
> Hi,
> 
> Context here :
> - 2 setups (2 datacenters) in oVirt 3.4.1 with CentOS 6.4 and 6.5 hosts
> - connected to some LUNs in iSCSI on a dedicated physical network
> 
> Every host has two interfaces used for management and end-user LAN
> activity. Every host also have 4 additional NICs dedicated to the iSCSI
> network.
> 
> Those 4 NICs were setup from the oVirt web GUI in a bonding with a
> unique IP address and connected to the SAN.
> 
> Everything is working fine. I just had to manually tweak some points
> (MTU, other small things) but it is working.
> 
> 
> Recently, our SAN dealer told us that using bonding in an iSCSI context
> was terrible, and the recommendation is to use multipathing.
> My previous experience pre-oVirt was to agree with that. Long story
> short is just that when setting up the host from oVirt, it was so
> convenient to click and setup bonding, and observe it working that I did
> not pay further attention. (and we seem to have no bottleneck yet).
> 
> Anyway, I dedicated a host to experiment, I things are not clear to me.
> I know how to setup NICs, iSCSI and multipath to present the host OS a
> partition or a logical volume, using multipathing instead of bonding.
> 
> But in this precise case, what is disturbing me is that many layers
> described above are managed by oVirt (mount/unmount of LV, creation of
> bridges on top of bonded interfaces, managing the WWID amongst the
> cluster).
> 
> And I see nothing related to multipath at the NICs level.
> Though I can setup everything fine in the host, this setup does not
> match what oVirt is expecting : oVirt is expecting a bridge named as the
> iSCSI network, and able to connect to the SAN.
> My multipathing is offering the access to the partition of the LUNs, it
> is not the same.
> 
> I saw that multipathing is talked here :
> http://www.ovirt.org/Feature/iSCSI-Multipath
> 
> I here read :
>>     Add an iSCSI Storage to the Data Center
>>     Make sure the Data Center contains networks.
>>     Go to the Data Center main tab and choose the specific Data Center
>>     At the sub tab choose "iSCSI Bond"
> 
> The only tabs I see are "Storage/Logical Networks/Network
> QoS/Clusters/Permissions".
> 
> In this datacenter, I have one iSCSI master storage domain, two iSCSI
> storage domains and one NFS export domain.
> 
> What did I miss?
> 
>>     Press the "new" button to add a new iSCSI Bond
>>     Configure the networks you want to add to the new iSCSI Bond.
> 
> Anyway, I'm not sure to understand the point of this wiki page and this
> implementation : it looks like a much higher level of multipathing over
> virtual networks, and not at all what I'm talking about above...?
> 
> Well as you see, I need enlightenments.
>