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From Simon Weller <swel...@ena.com>
Subject Re: database high availability question vs haproxy
Date Fri, 05 Jun 2015 13:18:04 GMT

Personally, I think that Gallera is always going to be a safer option, as it handles conflict
resolution natively. Having said that, it appears care has been taken in designing the ACS
MGMT DB integration so that the chance of conflicts is very low. Galera requires a 3 nodes
minimum, so it's a lot of hardware unless you've got plans to use it elsewhere in your organisation.

The downside to Galera, is that it's synchronous replication, so it needs very low latency
between nodes. That doesn't make it a good candidate for geographic separation between DB
nodes for a DR scenario.

You're understanding of the replication structure, as based on the design document is correct.
MySQL (or Galera) handles all the replication. ACS just handles which node it's writing and
reading from. In a 2 node native MySQL cluster, it's expected that you are setup for cross
master-master replication.

- Si
________________________________________
From: Andrija Panic <andrija.panic@gmail.com>
Sent: Friday, June 5, 2015 2:41 AM
To: dev@cloudstack.apache.org
Cc: users@cloudstack.apache.org
Subject: Re: database high availability question vs haproxy

Hi Simon,

thanks for the link - actually I have already read this - but Im still
seaking for some answeres :) :

- real world experience with DB HA in general  - is i better to use
haproxy(clustered/redudant) for mysql towards Galera cluster - or simply to
reference 2 nodes (1 as master, another as slave) with native ACS DB HA  -
silly question but anyway...
- my understanding - ACS just pings and connects to master or slave (all
replication etc, is done from my side, not from ACS) ?

Thanks again and any info is greatly appreciated.

Andrija

On 4 June 2015 at 16:23, Simon Weller <sweller@ena.com> wrote:

> Andrija,
>
> Here is the original design document, and it should give you a better idea
> of what is implemented today:
>
> https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=34838207
>
> We have plans to test this in our lab soon, but just haven't got around to
> it yet.
>
> - Si
>
> ________________________________________
> From: Andrija Panic <andrija.panic@gmail.com>
> Sent: Thursday, June 4, 2015 9:08 AM
> To: dev@cloudstack.apache.org; users@cloudstack.apache.org
> Subject: Re: database high availability question vs haproxy
>
> Anyone :) ?
>
> On 31 May 2015 at 00:26, Andrija Panic <andrija.panic@gmail.com> wrote:
>
> > Hi,
> >
> > I would have a question on database HA feature in db.properties (
> >
> http://cloudstack-administration.readthedocs.org/en/latest/reliability.html#configuring-database-high-availability
> > )
> >
> > If I understand correctly, it is up to the admin to provide appropriate
> > mysql HA (active-active, galera, etc) and ACS management server will
> JUST
> > try to connect to slaves if the master is down ?
> >
> > We are running Galera, with haproxy/keepalived, and by using stoping
> > haproxy, it takes i.e. 6sec for keepalived to detect haproxy is down, and
> > failover IP to another host.
> >
> > During these 6 seconds, ACS managemnt server goes dead, because of this
> DB
> > unavailability.
> >
> > So my wondering, is better to use ACS db HA feature, instead of
> > loadbalancer for this specific purpose ?
> > (we are also using haproxy/keepalived for management server loadbalancing
> > - 2 servers in backend...)
> >
> > Any experience shared is really appreciated !
> > --
> >
> > Andrija Panić
> >
>
>
>
> --
>
> Andrija Panić
>



--

Andrija Panić

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