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

2016-08-04 Thread 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 :

>
>
> On Thu, Aug 4, 2016 at 10:37 AM, James Michels <
> karma.sometimes.hu...@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 :
>>
>>> 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.hu...@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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Re: [ovirt-users] Fwd: Multipath iSCSI with several IPs

2016-08-04 Thread Dan Yasny
On Thu, Aug 4, 2016 at 10:37 AM, James Michels <
karma.sometimes.hu...@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 :
>
>> 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.hu...@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
>>>
>>> ___
>>> Users mailing list
>>> Users@ovirt.org
>>> http://lists.ovirt.org/mailman/listinfo/users
>>>
>>>
>>
>
>
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> Users@ovirt.org
> http://lists.ovirt.org/mailman/listinfo/users
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>
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Re: [ovirt-users] Fwd: Multipath iSCSI with several IPs

2016-08-04 Thread Alex Crow

On 04/08/16 15:37, James Michels wrote:


Hi Dan,

The way you describe it I should have 2 storage backends with 2 IPs 
for the same SAN backend, right? 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?



No, multipath is the *same* storage (ie LUN) exposed via two different 
network paths.


Alex

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