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From "Kelceydamage@bbits" <kel...@bbits.ca>
Subject Re: HA question
Date Thu, 28 Feb 2013 06:46:30 GMT
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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