Hello Genoveva
Yes, It's always a good idea to use our GA SVOS version on your hardware. If you need motivation, accessing the install base via our Cloud Portal Clear Sight(available at clearsight.hitachivantara.com) would give you insights in the security dashboard wrt vulnerabilities etc.
To answer your question, I'm a bit unsure on what you'd like to do exactly. You can use our virtualization technology UVM(Universal Volume Manager) to migrate volumes from 3rd party arrays to the Hitachi Arrays. The arrays you mentioned 350G and 5600 both support this and potentially using storage from the external storage as a external capacity pool. So both use cases Migrating volumes and using external storage as capacity for new volumes is supported. It's always a good idea to see if we tested it on our compatibility guide here:
https://compatibility.hitachivantara.com/products/uvm
If it's not on there it doesn't mean it wont work, it just means we haven't tested and certified it yet. Reach out to your Hitachi representative for help if needed:
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William Jansen Van Nieuwenhuizen
Hitachi Vantara
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