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From Nitin Mehta <Nitin.Me...@citrix.com>
Subject Re: HA question
Date Thu, 28 Feb 2013 07:51:10 GMT
I was searching for this document which used to be on docs.cloudstack.org
but couldn't find it. Thanks for pointing this one.

On 28/02/13 1:12 PM, "Mice Xia" <mice_xia@tcloudcomputing.com> wrote:

>There is a document describing HA in details, you can check it on:
>http://people.apache.org/~mice/CloudStackHighAvailability.pdf
>
>this document is a little outdated, but the concepts and overall workflow
>still apply.
>
>Regards
>Mice
>
>-----Original Message-----
>From: Kelceydamage@bbits [mailto:kelcey@bbits.ca]
>Sent: Thursday, February 28, 2013 3:24 PM
>To: cloudstack-dev@incubator.apache.org
>Cc: cloudstack-dev@incubator.apache.org
>Subject: Re: HA question
>
>I could get one started.
>
>I've saved this thread, and I'll try to get some stuff up in the next
>couple days.
>
>Sent from my iPhone
>
>On Feb 27, 2013, at 10:57 PM, Nitin Mehta <Nitin.Mehta@citrix.com> wrote:
>
>> 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.c
>>>>>>>> o
>>>>>> 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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