[ovirt-users] storage redundancy in Ovirt

[Dan Yasny]

On Sun, Apr 16, 2017 at 11:19 PM, Konstantin Raskoshnyi <konrasko at gmail.com>
wrote:

> Makes sense.
> I was trying to set it up, but doesn't work with our staging hardware.
> We have old ilo100, I'll try again.
> Thanks!
>
>
It is absolutely necessary for any HA to work properly. There's of course
the "confirm host has been shutdown" option, which serves as an override
for the fence command, but it's manual


> On Sun, Apr 16, 2017 at 8:18 PM Dan Yasny <dyasny at gmail.com> wrote:
>
>> On Sun, Apr 16, 2017 at 11:15 PM, Konstantin Raskoshnyi <
>> konrasko at gmail.com> wrote:
>>
>>> Fence agent under each node?
>>>
>>
>> When you configure a host, there's the power management tab, where you
>> need to enter the bmc details for the host. If you don't have fencing
>> enabled, how do you expect the system to make sure a host running a service
>> is actually down (and it is safe to start HA services elsewhere), and not,
>> for example, just unreachable by the engine? How do you avoid a splitbraid
>> -> SBA ?
>>
>>
>>>
>>> On Sun, Apr 16, 2017 at 8:14 PM Dan Yasny <dyasny at gmail.com> wrote:
>>>
>>>> On Sun, Apr 16, 2017 at 11:13 PM, Konstantin Raskoshnyi <
>>>> konrasko at gmail.com> wrote:
>>>>
>>>>> "Corner cases"?
>>>>> I tried to simulate crash of SPM server and ovirt kept trying to
>>>>> reistablished connection to the failed node.
>>>>>
>>>>
>>>> Did you configure fencing?
>>>>
>>>>
>>>>>
>>>>>
>>>>> On Sun, Apr 16, 2017 at 8:10 PM Dan Yasny <dyasny at gmail.com> wrote:
>>>>>
>>>>>> On Sun, Apr 16, 2017 at 7:29 AM, Nir Soffer <nsoffer at redhat.com>
>>>>>> wrote:
>>>>>>
>>>>>>> On Sun, Apr 16, 2017 at 2:05 PM Dan Yasny <dyasny at redhat.com> wrote:
>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> On Apr 16, 2017 7:01 AM, "Nir Soffer" <nsoffer at redhat.com> wrote:
>>>>>>>>
>>>>>>>> On Sun, Apr 16, 2017 at 4:17 AM Dan Yasny <dyasny at gmail.com> wrote:
>>>>>>>>
>>>>>>>>> When you set up a storage domain, you need to specify a host to
>>>>>>>>> perform the initial storage operations, but once the SD is defined, it's
>>>>>>>>> details are in the engine database, and all the hosts get connected to it
>>>>>>>>> directly. If the first host you used to define the SD goes down, all other
>>>>>>>>> hosts will still remain connected and work. SPM is an HA service, and if
>>>>>>>>> the current SPM host goes down, SPM gets started on another host in the DC.
>>>>>>>>> In short, unless your actual NFS exporting host goes down, there is no
>>>>>>>>> outage.
>>>>>>>>>
>>>>>>>>
>>>>>>>> There is no storage outage, but if you shutdown the spm host, the
>>>>>>>> spm host
>>>>>>>> will not move to a new host until the spm host is online again, or
>>>>>>>> you confirm
>>>>>>>> manually that the spm host was rebooted.
>>>>>>>>
>>>>>>>>
>>>>>>>> In a properly configured setup the SBA should take care of that.
>>>>>>>> That's the whole point of HA services
>>>>>>>>
>>>>>>>
>>>>>>> In some cases like power loss or hardware failure, there is no way
>>>>>>> to start
>>>>>>> the spm host, and the system cannot recover automatically.
>>>>>>>
>>>>>>
>>>>>> There are always corner cases, no doubt. But in a normal situation.
>>>>>> where an SPM host goes down because of a hardware failure, it gets fenced,
>>>>>> other hosts contend for SPM and start it. No surprises there.
>>>>>>
>>>>>>
>>>>>>>
>>>>>>> Nir
>>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Nir
>>>>>>>>
>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Sat, Apr 15, 2017 at 1:53 PM, Konstantin Raskoshnyi <
>>>>>>>>> konrasko at gmail.com> wrote:
>>>>>>>>>
>>>>>>>>>> Hi Fernando,
>>>>>>>>>> I see each host has direct connection nfs mount, but yes, if main
>>>>>>>>>> host to which I connected nfs storage going down the storage becomes
>>>>>>>>>> unavailable and all vms are down
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On Sat, Apr 15, 2017 at 10:37 AM FERNANDO FREDIANI <
>>>>>>>>>> fernando.frediani at upx.com> wrote:
>>>>>>>>>>
>>>>>>>>>>> Hello Konstantin.
>>>>>>>>>>>
>>>>>>>>>>> That doesn`t make much sense make a whole cluster depend on a
>>>>>>>>>>> single host. From what I know any host talk directly to NFS Storage Array
>>>>>>>>>>> or whatever other Shared Storage you have.
>>>>>>>>>>> Have you tested that host going down if that affects the other
>>>>>>>>>>> with the NFS mounted directlly in a NFS Storage array ?
>>>>>>>>>>>
>>>>>>>>>>> Fernando
>>>>>>>>>>>
>>>>>>>>>>> 2017-04-15 12:42 GMT-03:00 Konstantin Raskoshnyi <
>>>>>>>>>>> konrasko at gmail.com>:
>>>>>>>>>>>
>>>>>>>>>>>> In ovirt you have to attach storage through specific host.
>>>>>>>>>>>> If host goes down storage is not available.
>>>>>>>>>>>>
>>>>>>>>>>>> On Sat, Apr 15, 2017 at 7:31 AM FERNANDO FREDIANI <
>>>>>>>>>>>> fernando.frediani at upx.com> wrote:
>>>>>>>>>>>>
>>>>>>>>>>>>> Well, make it not go through host1 and dedicate a storage
>>>>>>>>>>>>> server for running NFS and make both hosts connect to it.
>>>>>>>>>>>>> In my view NFS is much easier to manage than any other type of
>>>>>>>>>>>>> storage, specially FC and iSCSI and performance is pretty much the same, so
>>>>>>>>>>>>> you won`t get better results other than management going to other type.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Fernando
>>>>>>>>>>>>>
>>>>>>>>>>>>> 2017-04-15 5:25 GMT-03:00 Konstantin Raskoshnyi <
>>>>>>>>>>>>> konrasko at gmail.com>:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> Hi guys,
>>>>>>>>>>>>>> I have one nfs storage,
>>>>>>>>>>>>>> it's connected through host1.
>>>>>>>>>>>>>> host2 also has access to it, I can easily migrate vms between
>>>>>>>>>>>>>> them.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> The question is - if host1 is down - all infrastructure is
>>>>>>>>>>>>>> down, since all traffic goes through host1,
>>>>>>>>>>>>>> is there any way in oVirt to use redundant storage?
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Only glusterfs?
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Thanks
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
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>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>
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>>>>>>>>>>
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