So just to make sure I follow:

  * I will want a distinct VLAN and IP address for each NIC acting as an
    iSCSI initiator.
  * In the middle the switch would be configured as basic access ports
    without any LACP.
  * Do I want the same for the target?  The QNAP docs say that for MPIO
    I would want to use their port trunking feature and a single IP for
    both NICs on that end, which confuses me as it seems to contradict
    the idea of two (or more) completely independent channels. 

As for how to get there, whatever exactly that might look like, I'm also
having troubles figuring that out.  I figured I would transform the
setup described below into one where each host has:

  * 2 NICs bonded with LACP for my ovirtmgmt and "main" net
  * 1 NIC for my 1st storage net
  * 1 NIC for my 2nd storage net

To get there though,  I need to remove the 4 existing logical storage
nets from my hosts, pull 2 NICs out of the existing bond and so on.  But
when I've attempted that, I get things into a funky state where the
hosts become non-operational because the old storage nets are
"required".  I unchecked that setting thinking that to be the right
path.  But I could never get much further towards the new setup because
the existing storage domain as all the old connections and I see no way
to "forget" them, at least through the engine -- I didn't try to fight
it behind its back with iscsiadmin to do session logouts.  Somewhere in
all this mess I got into a Catch-22 where I couldn't do anything with
the old SD because no host was suitable and no host could be made
suitable because the SD couldn't be connected.  I tried all sorts of
things of varying levels of scariness but wound up putting things back
to present for now since I clearly need some further advice.

One option that struck me as a possibility, but exceeded my risk
aversion threshold was to remove the storage domain entirely and create
a new one pointing to the same LUNs.  Is that what I need to do to
forget the old connections?  Is that safe to all my existing logical
disks, etc?  Does the engine just see an group of LUNs with oVirt
"things" and magically reconstruct it all from what's there?  I'm
guessing that's the case because I have recreated an engine before and
know that all the critical bits live in the SD, but I just want to be
sure I don't commit to something really boneheaded.

On 1/17/19 7:43 PM, Vinícius Ferrão wrote:
> MPIO by concept is when you have two dedicated paths for iSCSI.
>
> So you don’t put iSCSI inside LACP, because it won’t do the MPIO
> magic. Since it’s the same path with a single IP.
>
> The right approach is two subjects, completely segregated without
> routing. You can use the same switch, it will not be redundant on the
> switch part, but it will be on the connections and you have two paths
> to follow load balancing between them.
>
> But to be honest I never get how oVirt handles MPIO. The iSCSI
> Multipath button on the interface request that all points, on
> different paths, to be reached, which doesn’t make sense for my
> understanding. In the past I’ve opened a ticket about this but I
> simply gave up. Ended using XenServer instead for this case
> specifically, which I was trying to avoid.
>
> Sent from my iPhone
>
> On 17 Jan 2019, at 22:14, John Florian <jflor...@doubledog.org
> <mailto:jflor...@doubledog.org>> wrote:
>
>> I have an existing 4.2 setup with 2 hosts, both with a quad-gbit NIC
>> and a QNAP TS-569 Pro NAS with twin gbit NIC and five 7k2 drives.  At
>> present, the I have 5 VLANs, each with their own subnet as:
>>
>>  1. my "main" net (VLAN 1, 172.16.7.0/24)
>>  2. ovirtmgmt (VLAN 100, 192.168.100.0/24)
>>  3. four storage nets (VLANs 101-104, 192.168.101.0/24 -
>>     192.168.104.0/24)
>>
>> On the NAS, I enslaved both NICs into a 802.3ad LAG and then bound an
>> IP address for each of the four storage nets giving me:
>>
>>   * bond0.101@bond0: 192.168.101.101
>>   * bond0.102@bond0: 192.168.102.102
>>   * bond0.103@bond0: 192.168.103.103
>>   * bond0.104@bond0: 192.168.104.104
>>
>> The hosts are similar, but with all four NICs enslaved into a 802.3ad
>> LAG:
>>
>> Host 1:
>>
>>   * bond0.101@bond0: 192.168.101.203
>>   * bond0.102@bond0: 192.168.102.203
>>   * bond0.103@bond0: 192.168.103.203
>>   * bond0.104@bond0: 192.168.104.203
>>
>> Host 2:
>>
>>   * bond0.101@bond0: 192.168.101.204
>>   * bond0.102@bond0: 192.168.102.204
>>   * bond0.103@bond0: 192.168.103.204
>>   * bond0.104@bond0: 192.168.104.204
>>
>> I believe my performance could be better though.  While running
>> bonnie++ on a VM, the NAS reports top disk throughput around 70MB/s
>> and the network (both NICs) topping out around 90MB/s.  I suspect I'm
>> being hurt by the load balancing across the NICs.  I've played with
>> various load balancing options for the LAGs (src-dst-ip and
>> src-dst-mac) but with little difference in effect.  Watching the
>> resource monitor on the NAS, I can see that one NIC almost exclusive
>> does transmits while the other is almost exclusively receives. 
>> Here's the bonnie report (my apologies to those reading plain-text here):
>>
>> Bonnie++ Benchmark results
>>
>> *Version 1.97*       *Sequential Output*     *Sequential Input*      *Random
>> Seeks*       
>>      *Sequential Create*     *Random Create*
>>
>>      Size    Per Char        Block   Rewrite         Per Char        Block   
>> Num Files       Create
>> Read         Delete  Create  Read    Delete
>>
>>      K/sec   % CPU   K/sec   % CPU   K/sec   % CPU   K/sec   % CPU   K/sec   
>> % CPU
>>      /sec    % CPU   
>>      /sec    % CPU   /sec    % CPU   /sec    % CPU   /sec    % CPU   /sec    
>> % CPU
>> /sec         % CPU
>> unamed       4G      267     97      75284   21      22775   8       718     
>> 97      43559   7       189.5   8
>>      16      6789    60      +++++   +++     24948   75      14792   86      
>> +++++   +++     18163   51
>> Latency      69048us         754ms   898ms   61246us         311ms   1126ms  
>> Latency
>> 33937us      1132us  1299us  528us   22us    458us
>>
>>
>> I keep seeing MPIO mentioned for iSCSI deployments and now I'm trying
>> to get my head around how to best set that up or to even know if it
>> would be helpful.  I only have one switch (a Catalyst 3750g) in this
>> small setup so fault tolerance at that level isn't a goal.
>>
>> So... what would the recommendation be?  I've never done MPIO before
>> but know where it's at in the web UI at least.
>>
>> -- 
>> John Florian
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-- 
John Florian

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