The implementation of the virtualization solution is very simple and straightforward. The greater benefits are realized during the actual use of this system as the storage management function is greatly reduced. It would be very easy to implement a pilot configuration to see first hand the functionality, features, performance and reliability of the solution. There is so much hype and FUD about virtualization that you have to do quite a bit of homework yourself to determine the benefits of this technology. So which one is better than the other? In-band versus out-of-band?
You need to look at the synergy among all of the storage virtualization methods. You might need RAID sub-system virtualization for storing Windows documents, and in-band SAN virtualization for production databases on different platforms. To this end, you need you to ask yourself what are the problems you are trying to solve and how will the solutions contribute to the business value propositions. Take at a look at your environment requirements and then map them to the best of all of the virtualization methods. Factor in the service level requirements of your application to determine your best virtualization choices. Are there any other virtualization approaches besides "appliance based" or "software based"? What are the benefits of each?
These two storage virtualization methods raised a classic question: Which one is better
This would depend on how much existing infrastructure you already have, and whether or not you intend to have just your data replicated or would also have backup application and file servers at the remote site for site-failover purposes. It would also depend upon what vendors solution you pick. But I can say that a total solution for both sites, that is -- buying the storage and virtualization appliances -- can be found for around $0.15/M byte, list. If you have storage at both sites already, then it would be less. Wouldn't an in-band solution be a performance bottleneck or at least introducing some degree of latency? Are there any virtualization advances being made in hardware?
No, it's not going to be a bottleneck, because the appliance can be replaced with higher end server heads, with more PCI slots, allowing for a greater number of I/O in (from the storage) and I/O out (to the hosts), plus aggregate performance gains from the fact that two heads would be clustered in an active/active failover configuration. There are high end servers now that offer 10 PCI-X 64 bit slots without shared bandwidth, that can support Quad Port 1G bit Fibre Channel and Dual Port 2G bit FC HBA's, so in the case of the server I just mentioned, you could have 2000M Bytes/sec throughput managed by a single server. Beyond that it's simply a matter of adding another pair of clustered servers, and then another pair, etc. For the SAN over IP functionality, you will be able to take advantage of future technology, such as Infiniband or 10G bit Ethernet. As far as latency is concerned, because of queue depth functionality and I/O load balancing the solution can give you a gain over any latency. This is measurable, even if it is not a practical amount. Will virtualization solutions decrease the reliance of tape?
No. Backup/restore will still be required as your policies are established within your organization today. It is always sound practice to backup to tape no matter what other experts say. What virtualization brings to the table are much faster backup speeds as well as elimination of back-up windows as the backups are done in the background. Virtualization solutions do have the features to mirror and/or replicate your data over a LAN/WAN/MAN. What is the minimum company size that can afford virtualization?
The question is better asked by can even a small company not afford a virtualized system. The initial hardware and software cost to annual management costs are 1:6. So the expense is not in the initial purchase but the on going personnel cost. With the right in-band solution (not that there are wrong ones, just some have features that would impact these costs and others may not) these costs can be cut considerably.