[ovirt-users] Fwd: Multipath iSCSI with several IPs

[James Michels]

Nice, now it's crystal clear. This is an Huawei Oceanstor disk array which
we want to test with ovirt so we can see performance, how ovirt behaves
with situations where one controller is disconnected etc., that's why we
wanted to implement multipath.

Thanks for the insight!

James

2016-08-04 15:42 GMT+01:00 Dan Yasny <dyasny at gmail.com>:

>
>
> On Thu, Aug 4, 2016 at 10:37 AM, James Michels <
> karma.sometimes.hurts at gmail.com> wrote:
>
>> Hi Dan,
>>
>> The way you describe it I should have 2 storage backends with 2 IPs for
>> the same SAN backend, right?
>>
>
> Every iSCSI SAN has multiple portals (usually one on each storage
> controller, and each with it's own IP), and when you create a target you
> assign it the portals through which it should be accessible. So if you have
> two portals (two IPs) assigned to a target (LUN), you can access it via two
> paths, each path leading through a different portal/IP to the same
> target/LUN.
> What do you use for your iSCSI backend?
>
>
>> The problem I see is that when you create a disk for a VM, you assign it
>> to only one storage domain... so if the first fails, how will oVirt know
>> which one should use as failover?
>>
>>
> There is only one disk, but it sits on a target, which can be accessed via
> two different IPs. oVirt stores all the iSCSI portal IPs you give it as
> described in my first response in a database, and connects to them when
> connecting to the storage domain. If one is down, multipath will mark the
> path as down and keep using other IPs to access the same LUN
>
>
>> Thank you
>>
>> 2016-08-04 15:20 GMT+01:00 Dan Yasny <dyasny at gmail.com>:
>>
>>> Normally you
>>> 1. enter the IP
>>> 2. click discover
>>> 3. login to whatever was found
>>> 4. enter another IP instead of the first
>>> 5. goto 2
>>>
>>> On Thu, Aug 4, 2016 at 10:13 AM, James Michels <
>>> karma.sometimes.hurts at gmail.com> wrote:
>>>
>>>> Hello,
>>>>
>>>> I want to add an iSCSI based storage domain. For that I add a domain on
>>>> the Storage tab with one of the IPs (say 10.10.10.1), but for failover
>>>> purposes I'd like to use multipath to add a failover IP so if the first one
>>>> fails, LUNs can be reached via the second (say 10.10.10.2).
>>>>
>>>> How can this be done in oVirt 4.0.1? I have not seen a way how to add
>>>> the second IP for multipath purposes.
>>>>
>>>> Thank you
>>>>
>>>> James
>>>>
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>>>>
>>>
>>
>>
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