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From Nitin Mehta <Nitin.Me...@citrix.com>
Subject Re: HA question
Date Thu, 28 Feb 2013 06:57:31 GMT
Kelcey - Would you be willing to put a HA wiki ? I promise to volunteer :)
with whatever I know

On 28/02/13 12:16 PM, "Kelceydamage@bbits" <kelcey@bbits.ca> wrote:

>This is turning out to be a great discussion to have. Now I get that
>CloudStack HA is purely handled by the  management/orchestration engine
>and only if VM is tagged(which I knew). But what is good to find out is
>that it does not involve underlying hypervisor specific HA modules(except
>perhaps VMware). Incidentally VMwares HA mechanism is also called storage
>heartbeat(5.x+) but it uses hypervisor modules as well.
>
>I do agree with Ahmad that it might be worth looking into expanding our
>HA suite to support hypervisor specific HA modules as an override to the
>default CS HA.
>
>There has not been too many HA discussions on the mailing list, and by
>the looks of it we were all under slightly different impressions.
>
>Thanks again for the good discussion.
>
>Sent from my iPhone
>
>On Feb 27, 2013, at 9:48 PM, Ahmad Emneina <aemneina@gmail.com> wrote:
>
>> I would imagine it's best to leverage on the underlying hypervisors' HA
>> mechanisms, configured oud-of-band of cloudstack. I find cloudstacks
>> implementation a little laggy compared to the paid for variety.
>>CloudStack
>> does a well enough job to figure out which host the vm eventually lands
>>on.
>> 
>> 
>> On Wed, Feb 27, 2013 at 9:37 PM, Mice Xia
>><mice_xia@tcloudcomputing.com>wrote:
>> 
>>> Currently for xenserver/KVM, Cloudstack uses 'storage heartbeat' to
>>>detect
>>> whether it should start HA, i.e. agent resides on xenserver/KVM
>>> periodically writes a timestamp on shared storage, if host network
>>> pingTimeOut happens, Cloudstack will investigate if 'storage heartbeat'
>>> timeout and if that's the case HA job will be launched for HA enabled
>>>VMs
>>> on the host.
>>> 
>>> It's a simplified procedure, HA implementation involves delta sync/
>>> investigators and fencers.
>>> 
>>> -Mice
>>> 
>>> -----Original Message-----
>>> From: Sanjeev Neelarapu [mailto:sanjeev.neelarapu@citrix.com]
>>> Sent: Thursday, February 28, 2013 1:21 PM
>>> To: cloudstack-dev@incubator.apache.org; kdamage@apache.org
>>> Subject: RE: HA question
>>> 
>>> Hi Hari,
>>> 
>>> AFAIK, in CloudStack if a host crashes CloudStack would detect the
>>>host as
>>> down after pingTimeout interval.
>>> CloudStack does not reduce the available capacity because the host
>>> capacity values are not removed from op_host_capacity table. It
>>>assumes the
>>> host down is a temporary issue.
>>> 
>>> Thanks,
>>> Sanjeev
>>> 
>>> -----Original Message-----
>>> From: Hari Kannan [mailto:hari.kannan@citrix.com]
>>> Sent: Thursday, February 28, 2013 10:36 AM
>>> To: kdamage@apache.org; cloudstack-dev@incubator.apache.org
>>> Subject: RE: HA question
>>> 
>>> Hi Kelcey,
>>> 
>>> At the risk of stating the obvious, I just wish to re-iterate my
>>>earlier
>>> point - with CloudStack, HA is for VM, not for host. That is different
>>>than
>>> VMware's HA in someways - in VMware, if a cluster is HA, when any host
>>> crashes, all VMs on that host will be restarted on a different host.
>>>With
>>> cloudstack, only VMs that are HA enabled will be restarted.
>>> 
>>> At least, that is the way I understand this..
>>> 
>>> I also wonder what happens in CloudStack if a host crashes (assume
>>>there
>>> were no VMs on it) - would CloudStack detect this host is down and
>>>reduce
>>> the available capacity?
>>> 
>>> Hari
>>> 
>>> -----Original Message-----
>>> From: Kelcey Damage (BT) [mailto:kelcey@backbonetechnology.com] On
>>>Behalf
>>> Of kdamage@apache.org
>>> Sent: Wednesday, February 27, 2013 8:51 PM
>>> To: cloudstack-dev@incubator.apache.org
>>> Cc: Hari Kannan
>>> Subject: RE: HA question
>>> 
>>> So it's safe to conclude that HA while enabled on the host(As in the
>>> module), must be available cluster wide(uniform cluster). This is how
>>> VMware and others operate.
>>> 
>>> Thanks all.
>>> 
>>> -Kelcey
>>> 
>>> 
>>>> -----Original Message-----
>>>> From: Sateesh Chodapuneedi [mailto:sateesh.chodapuneedi@citrix.com]
>>>> Sent: Wednesday, February 27, 2013 8:46 PM
>>>> To: cloudstack-dev@incubator.apache.org
>>>> Cc: Hari Kannan
>>>> Subject: RE: HA question
>>>> 
>>>> For VMware, CloudStack uses native HA provided by VMware.
>>>> VMware provides HA at the level of cluster.
>>>> 
>>>> Regards,
>>>> Sateesh
>>>> 
>>>>> -----Original Message-----
>>>>> From: Nitin Mehta [mailto:Nitin.Mehta@citrix.com]
>>>>> Sent: 28 February 2013 10:13
>>>>> To: cloudstack-dev@incubator.apache.org
>>>>> Cc: Hari Kannan
>>>>> Subject: Re: HA question
>>>>> 
>>>>> CS has its own HA logic and doesn't use the native HA of the HV and
>>>>> so the question for enabling the HA for hosts doesn't arise. This is
>>>>> true
>>> for XS.
>>>>> For Vmware and KVM, I will let the guru's speak :)
>>>>> 
>>>>> On 28/02/13 9:55 AM, "kdamage@apache.org" <kdamage@apache.org>
>>>> wrote:
>>>>> 
>>>>>> Thanks that¹s awesome, but not quite the answer I was looking for.
>>>>>> 
>>>>>> To better phrase my question, if the cluster is the basic unit of
>>>>>> availability, when hosts are enabled for HA, must all hosts in the
>>>>>> cluster be enabled? Or can the cluster exist with a non-uniform
>>>>>> structure, having only some hosts enabled for HA?
>>>>>> 
>>>>>> You partially answered it with the special reserve HA hosts, but
I'm
>>>>>> looking more in terms of general use.
>>>>>> 
>>>>>> Thanks
>>>>>> 
>>>>>> -kelcey
>>>>>> 
>>>>>> 
>>>>>>> -----Original Message-----
>>>>>>> From: Hari Kannan [mailto:hari.kannan@citrix.com]
>>>>>>> Sent: Wednesday, February 27, 2013 8:21 PM
>>>>>>> To: cloudstack-dev@incubator.apache.org
>>>>>>> Subject: RE: HA question
>>>>>>> 
>>>>>>> Hi Kelsey,
>>>>>>> 
>>>>>>> HA is at 2 levels ­ VMs can be marked HA. In addition, you can
mark
>>>>>>> some hosts as reserved for ³Dedicated² HA hosts. Quoting from
the
>>>>>>> manual, the dedicated HA option is set through a special host
tag
>>>>>>> when the host is created.
>>>>>>> To allow the administrator to dedicate hosts to only HA-enabled
>>>>>>> VMs, set the global configuration variable ha.tag to the desired
>>>>>>> tag (for example, "ha_host"), and restart the Management Server.
>>>>>>> Enter the value in the Host Tags field when adding the host(s)
that
>>>>>>> you want to dedicate to HA-enabled VMs.
>>>>>>> 
>>>>>>> Hari
>>>>>>> 
>>>>>>> From: Kelcey Damage (BT) [mailto:kelcey@backbonetechnology.com]
>>>>>>> Sent: Wednesday, February 27, 2013 8:00 PM
>>>>>>> To: CloudStack dev list
>>>>>>> Subject: RE: HA question
>>>>>>> 
>>>>>>> Hi,
>>>>>>> 
>>>>>>> I can¹t remember, do we enable HA on a per host basis, or on
a per
>>>>>>> cluster basis?
>>>>>>> 
>>>>>>> Thanks.
>>>>>>> 
>>>>>>> [cid:image001.png@01CE1524.FA0D61B0]Kelcey Damage Infrastructure
>>>>>>> Systems Architect
>>>>> 
>>>>>> www.backbonetechnology.com<http://www.backbonetechnology.com/>
>>>>>>> -------------------------------------------------------------------
>>>>>>> -
>>>>>>> -----
>>>>> 
>>>>>> kelcey@backbonetechnology.com<mailto:kelcey@backbonetechnology.co
>>>> m
>>>>>>>> 
>>>>>>> 
>>>>>>> address: 55 East 7th Ave, Vancouver, BC, V5T 1M4
>>>>>>> tel: +1 604 713 8560 ext:114
>>>>>>> fax: +1 604 605 0964
>>>>>>> skype: kelcey.damage
>>>>>>> 
>>>>>> 
>>>>>> 
>>> 
>>> 
>>> 

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