The Importance of Reboot Order

 

iStock_000007956082SmallIf you have ever had a planned power outage for building maintenance or needed to reboot your core networking switch, you have most likely had to power down the servers and other machines in your environment.  The order that those machines are powered down and back up may not see important, but if not done properly, it can cause issues.

Every environment is different, but also similar.  You may have physical servers, virtual servers on ESXi hosts, SAN or other network storage working together to build your company’s systems.  Some of these different components are dependent on one another.  It may be that the VMs on your hosts are using datastores on a SAN or that your web server needs the SQL database that is stored on another server to start up your sites.  These dependencies are the reason the reboot order is so important.  As long as you keep the dependencies in mind, you should be able to get a good procedure in place in the case that your environment needs to be powered down for any reason.

If you do need to do this, start with the VMs.  Begin powering down all of your virtual servers.  You will want to save the vCenter and DCs for last.  If you don’t have a DC running, you won’t be able to log into the other servers to gracefully shut them down.  Once all of the servers are powered down, you can move onto the hosts.  Those hosts may be relying on storage if it is not local storage within them.  That is what you will shut down last, after anything that may be attached to it is powered off and no longer using the storage system.

To bring everything back up, just go in the reverse order.  Storage system first, followed by the hosts.  Once the hosts are online, you can bring up your vCenter and DCs so that other machines authenticate properly when coming back online.  Keep the dependencies in mind when bringing up the individual servers.  If you have a server that relies on a SQL database, be sure to bring up your SQL server first.  Confirm that everything has come back up properly by testing your applications and data availability.

 

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