I think latest news and release surrounding SPARC changes the economy quite a bit. You will now get Virtualization with LDOM and Zones, Solaris and management with OpCenter included in your support contract.
This comes as the same time as the SPARC T4 is released with is suitable for a wide range of workloads contrary to the previous generations on T-series. The new T4 systems are also much cheeper compared to M-series with the same amount of compute power.
The included encryption also seems to be the fastest currently available in a common processor, so you can get the benefit of encrypting your filesystem/database/network with a very small performance penalty.
Compared to a few month ago the list of good news is quite impressive:
- SPARC T4 with 5x the single thread performance of SPARC T3
- 2-3x times faster encryption compared to T3 (which already was fast)
- Live migration of LDOMs
- OpCenter included in support contact
- Live migration between T2,T3 and T4 in the near future
- T4 supports 256GB memory per socket (1TB for the 5U T4-4)
- A engineered system is available, the SPARC SuperCluster
- Solaris 11 will be released shortly
Compared to other virtualization technologies Solaris Zones has no overhead and VM for SPARC (LDOM) have no overhead for CPU or memory. Some presentations at OOW claimed that zones had 4x less latency than KVM and 15x lower overhead compared to VMWare.
The next generation of T-processor is also being developed and should arrive next year. They will double the number of cores to 16 per CPU. A possible T5-4 would have 64 cores and 512 threads in one 5U enclosure.
I know there is a lot of talk about supporting the whole stack, but you will have one single vendor to blame for problems with the server, virtualization and management. Perhaps more importantly it will not cost more than the hardware itself and the support contract.