latest v7 vs v8 vs v9 firmware?

I always read the release notes first.  Plus you need to consider if you have any special compatibility scenarios.  For example I had servers running an older version of Citrix XenServer using a feature that integrated native Equallogic support to dynamically create and manage native iscsi volumes inside the xencenter interface.  They have made that software end of life so support for newer equallogic firmware versions is no longer maintained.  I had to keep the array at the older version 5.2.5 until I had the ability to export the virtual machines to temporary storage and basically reformat everything and then import the machines again using the new equallogic setup recommendations that uses a more generic shared iscsi volume rather than dedicated iscsi for each VM when I upgraded to the most recent Xenserver that no longer had the native equallogic support built in.

If you are sticking with common setup scenarios you likely will not have any special compatibility issues but still check the release notes for anything that might affect you.  If you have concerns it's a good idea to open a support case to discuss the upgrade impacts with Dell.  

In general I usually avoid the latest and greatest firmware version (9.x) until it's been out for a long time or it has a specific new feature that gives you some benefits.  In particular I believe version 9 is of most interest to someone who has a mixture of compellant and equallogic arrays as it now has more integration options for replication with version 9.  If you do not need those features it wouldn't provide much benefit and I would stick with version 8.1 for now.  Version 8 new feature mostly have to do with expanding the number of VMWare virtual volumes you can create.  Again, if you only use Hyper-V or another platform then version 8 likely wouldn't provide any major benefits but at this point it's gone through many releases and would be considered very mature and stable.  If you have older arrays in your group you might be restricted from upgraded to version 8 if it's at or near it's end of life so does not support version 8 and then you probably need to stay on version 7 until you either upgrade to new model or remove the old members from the group.

Hello, 

 There is another reason to stay more current, besides new features, fixes.  9.x and 8.1.x are the active firmware code streams.  There won't be any more 7.x, 6.x, etc releases.   Also, the current release often has fixes that haven't been back ported to the earlier release yet..  Based on the timing of the release.  Also sometimes there are fixes that can't be back ported to the earlier release.   9.0.0 EPA was released in April I believe, so it has been out there for a while and quite a few customers have moved to it already. 

Yeah the XenServer Storage Link software issues was a shame.  Citrix wrote the adapter code themselves and did the certification as well.  

 I do agree that reading the release notes is a great idea. 

Regards, 

Don