Netbackup media server virtualisation, multi-tenancy etc - best practices.
Lots of question - I expect you will get a lot of answers from different users with different views in this thread :-D
1: Symantec/Veritas don't have a recommendation. In my view using VM's or physical is a question of performance, price and usage.
2: You can if performance allow. But do some math on the number of times traffic passes forth and back. Also beware that debugging VM performance issues can be very hard because of the virtual layer.
3: In my view it don't make sense increasing number of VM when the underlying hardware is maxed out.
4: yes, no problem
5: I use physical server for multiple customers. I do not have a security problem with that, but please spend some time on the number of VM you may need when scaling. Also do you have secuirty staff in house with diffrent views. Firewall where traffic pass ?
My own comment: I use physical servers for everything, but gain I work large scale (last I checked the counnter it said 700TB/24h). I do have master media servers VM in small remote location. But not in the primary data centers. The bottom line in this is - fine to use VM when workload permits - but dont force VM just becuase the strategy say "VM". A mixed match may be what you need.
I'm not aware of any guidelines. My own gut feel is to go with with fewer but more gruntier virtualised NetBackup Media Servers - with more vCPUs there should be less process context switching, and more chance that a process will continue with CPU 'quantum time slicing' for longer (i.e. stay 'current on CPU' and not be moved off to a 'waiting for compute' resource wait state).
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Will these 'Media Server' VMs also be doing de-dupe? I can't quite put my finger on it, but it just doesn't sound right to me. I'm left with a disquieting sense of unease about supposedly big'n'beefy virtualised Media Servers. IMO de-dupe needs a really really fast 'bus' between CPU and RAM - in de-dupe land there is just so much data moving around between RAM and CPU (for hash fingerprinting (and encryption at rest)) that, IMO, only a physcal server can cut the mustard. Here's a question... Why do Symantec not 'sell' a 'VM appliance'? I bet they've checked it out... easy package... easy sell... easy money... but poor performance... unhappy customer... bad press.
And - why is there no 'word on the street' (i.e. on here, in this forum) regarding success stories of large installations of virtualised 'backup data movers'. In fact, why do the other backup vendors also push tin and not pre-packaged VM appliances?
The more I think about this, the less I like it. And, I've never seen any whitepapers extolling the virtues of virtualised media servers.
I would suggest a look at page 5 of tis document:
Statement of Support for NetBackup 7.x in a Virtual Environment (Virtualization Technologies)
http://www.symantec.com/docs/TECH127089
For all Virtualized environments, there is the inherent overhead of the hypervisor layer between the guest OS and the VM installed software. When using phyusical hardware, the OS and all applications are running directly on the physical hardware itself. In a virtualized envieonment, the OS running on the hardware is the virtualization OS, pplus hypervisor which translates the normal OS API calls from what the guest OS thinks it is using to what the hardware itself is using,. The code path length is longer to address the API calls.
Running on a physical server also means it is not sharing the hardware resources amonst other applications or guest OS instances.
