Hello and welcome to the communities.
Question 1:
There is the ESX version? And now there is only the ESXi version? I tried downloading the ESX and found I can just see the ESXi 5.5 .
There is no longer ESX. It is all ESXi now.
Question 2 :
If not longer more ESX version , as we do with ARCserve Backup to perform you need to install the agent to perform bakcup virtual machines ?
You will need to update ARCserve to a newer version. They have an option that can backup full VMs or you can use the agented in-guest approach.
Question 3 :
In my environment I have 5 VMWares hosts , each with a different version and some with others with ESX4 and ESXi 4 . I am installing a new machine with ESX5.5 to use the HA cluster .
What is recommended ? Upgrade these machines with older versions to 5.5 ? In the case of ESX4 , I'll have to upgrade to ESXi 5.5 ?
Or no need to upgrade , suffice to include this new vCenter and create the HA cluster ?
You will need vCenter Server 5.5 to manage ESXi 5.5 - it can also manage your ESX/ESXi 4.x hosts. Check the VMware Product Interoperability Matrixes for support information here.
Question 4 :
Any recommendations for the use of virtual machines with iSCSI , knowing that thopout is much smaller than a FC (Fiber Chanel ) ? Ie keep od VMDKs OS on RAID place and the other unit in the datastore with ISCSI ? Any tips on best practice?
This depends on a lot of factors, and implementing these practices adds complexity. I like to, as a general rule, place all VM files in a single datastore to start with. What iSCSI storage are you using, as the vendor recommended best practices are probably where you will want to look here.
Question 5 :
If I wanted to upgrade from version 4 , which is better ? Make updates 1 , 2 , 3 ... or make direct upgrade to version 5 ?
Direct upgrade where applicable, or even better is a fresh install of 5.5. Again - if complexity isn't too bad here.
