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From Andrew Robertson <andyrobertson...@gmail.com>
Subject Re: Multiple CentOS versions in same stack?
Date Thu, 14 Jan 2016 15:33:27 GMT
Thanks for the feedback!

Our test cluster is Centos6 VM-based, and I may spin up a new Centos7
VM in that to see how well it behaves at some point.  Our primary
cluster is bare-metal, and spinning up a new cluster == doubling the
number of machines in the cluster == very expensive; so that's not
option for us.

With centos6 moving into a long-term update phase that isn't expected
to support some new hardware (as of q2 2016)[*] and later no new
hardware (as of q2 2017) there may be an increased need to support
this upgrade path as well.

Would it be worth opening a JIRA to request this support as an actual
feature so the various actions on the clusters gets tested?

[*] https://access.redhat.com/support/policy/updates/errata/#Life_Cycle_Dates
-- this is redhat, but centos6 follows the redhat6 lifecycle/patches


On Thu, Jan 14, 2016 at 6:54 AM, Sumit Mohanty <smohanty@hortonworks.com> wrote:
> As far as I remember, when installing a cluster you can choose a cluster with mixed OS.
Ambari can pick the correct repo based on the OS. However, as Greg said, for an installed
cluster it may be a different issue. In general, centos6 and centos7 repo contents are compatible
but I am not 100% sure.
>
> One path to try is to do an Add Host with centos7. I expect Add Host to pick the right
repo URL based on the OS. If you must use local repo then you need to edit the already stored
repo details in the DB to make sure that centos7/rhel7 one is pointing to your local centos7
repo. If the above works as expected then you can try Remove Host/Upgrade/Add Host for the
Slave nodes. Its just that you need to remember what components are deployed on the host and
add those back.
>
> For master services, Remove/Add hosts do not work well especially for NameNodes. But
NameNode can be moved.
>
> Another option is to Add a Slave host with CentOS6 and then upgrade and see what more
is needed to get that to work. If this option works for you then it might be the fastest way
to upgrade the OS. Assuming no binary issue, this option may require modifying CentOS7 repo
to be the same as the CentOS6 repo in the Ambari DB and repoinfo.xml files.
>
>>> Your best option is probably to spin up a new cluster with the new OS and migrate
the data.
> +1 to this option
> ________________________________________
> From: Greg Hill <greg.hill@RACKSPACE.COM>
> Sent: Thursday, January 14, 2016 6:37 AM
> To: user@ambari.apache.org
> Subject: Re: Multiple CentOS versions in same stack?
>
> Honestly, I don't know that anyone has ever tried, but I have a feeling it
> might not work out well.  The 'repo' is specified at the stack level, so
> you'd have to make a new cluster after modifying the repo url on the stack
> in order for the new nodes to even know to use a different repo from the
> old nodes for installing packages.  Also, the os_family and os_type is in
> the ambari-server configs and isn't overrideable per-node, unless there's
> some hidden feature I'm not aware of.
>
> Your best option is probably to spin up a new cluster with the new OS and
> migrate the data.
>
> Greg
>
> On 1/13/16, 6:20 PM, "Andrew Robertson" <andyrobertson101@gmail.com> wrote:
>
>>Has anyone ever tried to run an Ambari cluster with hosts at different
>>centos versions (or some nodes with one OS like centos and other nodes
>>with something else?)
>>
>>Any reason this wouldn't be advised?
>>
>>I'm considering upgrading from centos 6 -> centos 7.  Given the
>>current centos 6 -> 7 upgrade path is "reinstall", this make take some
>>time to accomplish and I'd end up with a mix of both machine types in
>>the cluster during this time.
>>
>>I don't see any reasons this would not work - but I also don't see
>>anything that explicitly states this is a tested/advised config
>>either.
>>
>>Thanks!
>

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