I tell once more - VSS is windows technology and I dont have windows there in VM. And even when I have windows, VSS cant do nothing with 3rd party servers or databases.
Yes, VSS is a Microsoft technology, but it's only one implementation of quiescence. There are others as I've stated. Also, what do mean by by "3rd party servers or databases"? Databases made by Microsoft? Because that's also not true. Any software vendor can write a writer that responds to VSS commands. The fact that it isn't sold by Microsoft makes no difference.
I can just make VM snapshot with memory. Then make storage SAN snapshot for that LUN. Then make storage SAN snapshot replication to another SAN or to different storage pool in the same SAN. This is very fast operation, integrated into storage hardware, uses CBT (changed block tracking). Then I can delete storage SAN snapshot of LUN. Then I can delete vmware VM snapshot. Also, hardware storage SAN have also automation for all this. It have sheduling and also vmware compatible snapshot agent. And I dont need any writer at all.
Fine, if that works for you because you're using Linux and your software vendor is crap, then great. Glad for you. But have you ever tried restoring a VM to a powered-on state and that VM runs some sort of database application? If not, let me just tell you that most of the time when you restore to this point, you have to reboot the VM anyway because it's unstable. But, as I said, if you are using some obscure software made by a vendor that won't provide proper backup methodologies including quiescing scripts, then more power to you. I wish you luck.
So, you dont know what is embedded VM? In OVF or OVA format? They are not physical, they are virtual. And yes, any influence to its operating system is prohibited. If you talk to support that you insert something into operating system, then support first request you to delete whole VM and install pure plain one. Because this kind of action is not supported and allowed. Its hacking and against of license. There is no Oracle, most server databases are unique, only made for this software, there is no standard. Only external databases are standards.
Once again, this is a problem you're having with whatever software or system vendor you're dealing with who refuse to provide any safe and reliable backup methodologies. You're blaming other vendors for not supporting a method to quiesce these types of applications/systems when the blame is on the vendor who sold it to you. You need to go to them and complain rather than to all other backup application vendors and complain. It's not their responsibility to support obscure, poorly-written apps or operating systems--especially pre-built and packaged virtual appliances.