Upgrade a multi-server setup from PureMessage 6.2.1 to the lastest version

Question

Hello, 
 
 I have several questions regarding a PureMessage upgrade, from 6.2.1 to the latest, on a multi-servers setup (2 backends, 4 front-ends), looking for some feedback/experience abouit upgrades. 
 
 - Anyone can tell me if this kind of upgrade is risky? I just plan to break the disks mirrors, and span the upgrade over 2 days. 
 - My company chose to install pmx in a non standard location, but still under a signe tree (/appli/pmx). The documentation recommends not to change it, will the upgrade work? Should I do a bind mount to /opt/pmx to ensure defaults paths are still available? 
 - The documentation ( https://docs.sophos.com/msg/pmx/help/en-us/msg/pmx/tasks/GSGUpgradeMultiServers5.0.html) give an order (CSM, MTA, EUW) to respect, but will the components be able to work together between the upgrades? Will there be an outage, for instance can the MTA component connect to an upgraded backend? 
 - Will the upgrade of the 2 backend work straightforward (one after the other that is)? Can 2 versions cohabitate at some point (in order to keep the cluster working)? 
 
 Thank you in advance. 
 
 Kind regards, 
 
 Charles-Antoine

Red_Warrior · Answer

Hi Charles, 
 I recommend checking with your account manager and seeing if you have available pro-services time. If so, I would consult them for the upgrade. 
 unfortunately the amount of information needed can not be conveyed through the community forum. 
 
 however here are some general notes. 
 perform full backups of any hosts to be upgraded. (pmx lives in /opt/pmx6 by default but you can install it anywhere) a key thing to note is the location of your mta.. if your using the bundled version then it should be in the opt/pmx6/ directory. If your using your own.. 
 usually the csm is upgraded first then the edge servers.. all servers should be on the same version 
 as for front/back end servers, pmx has no idea about that.. it simply checks the transport file / rules to find out if a mail is inbound or outbound. If you have some funky routing going on or front/back end servers thats unique to your environment. 
 
 in a very general sense you should not have any problems upgrading from anything higher than 6.0.1 to current by running the pmx script from /opt/pmx6/etc as root with environment. 
 
 if you are running redis and have delay queue configured you may need to upgrade via tarball to 6.4.0 first (this will install the framework and db schema properly) then additional upgrade to the newest version will be applied. 
 
 also review the know issues and release notes to make sure there is nothing critical to your environment that may be affected 
 http://pmx.sophos.com/rn/pmx/concepts/KnownIssues.html 
 
 again, 
 if in doubt I strongly recommend discussing your environment with the PS team or contact your account manager to get a hold of them.