Do we need to upgrade the onefs version before adding new node to existing cluster

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The OneFS version would be automatically down graded or upgraded to match the OneFS on cluster.

Node and Disk firmware will not be synced and would need a manual check AFTER adding into cluster if upgrade is needed.

something more to consider:

some of the nodes need a specific release to work

X210 / S210 Need at least 7.2.1.x . Otherwise they are not supported.

Furthermore DellEMC thinks it is a very good idea to only guarantee the compatibility of new hardware to Target Code and Target Code -1. So if you buy some more nodes you should better be at Target or Target -1. Otherwise you might have luck and it is compatible. or you might not have luck and have to upgrade first.

To add to sluetze 's response:

Here is the Isilon Support and Compatibility Guide to assist you with researching compatibility:

https://support.emc.com/docu44518

As well as the Current Isilon Software Releases:

https://support.emc.com/docu46145

Please note that the recommendation stated above was Target Code and not General Availability Code. The difference is explained in the document.

If they're only adding one node, I would assume the hardware is identical to the other nodes in the cluster, otherwise... so there shouldn't be a problem with the version number.

x200 Cluster +x210 in compat mode would also be an possibility. but yeah, this shouldn't be his case, since he is "new" to the isilon and thus the isilons should be new too.