A tale of two CPU architectures

AMD Opteron Intel XeonLast week I wrote about the VMware infrastructure that I’m trying to put in place. I mentioned that my testing has been based on HP ProLiant DL585 servers – each of these is equipped with four dual-core AMD Opteron 8xx CPUs and a stack of memory. Half of the initial infrastructure will use new DL585s and the intention is that implementing these servers will release some recently-purchased HP ProLiant DL580G3s for an expansion of the infrastructure. Because the DL580G3 uses an Intel Xeon MP (formerly codenamed Paxville MP) processor, the difference in processor families requires a separation of the servers into two resource pools; however that’s not the real issue. My problem is justifying to an organisation that until now has exclusively used Intel processors that AMD units provide (as my CTO puts it) “more bang for our buck”.

The trouble is that the press is full of reports on how the new Intel Xeon 51xx CPUs (formerly codenamed Woodcrest) out-perform AMD Opterons, where AMD has been in the lead until now; but that’s in the 2-processor server space and I’m not hearing much about 4-way units.

All of this may change tomorrow as, at today’s VMware Beyond Boundaries virtualisation roadshow, Richard Curran, Director of Marketing for the Intel (EMEA) Digital Enterprise Group, hinted about an impending announcement; however an HP representative expressed a view that any new CPU will just be to plug the gap for a few months – the real performance boost will come in a few months time with the next generation of dual-core multiprocessor chips (in the same way that the Xeon 50xx chips, formerly codenamed Dempsey, preceded the 51xx Woodcrest).

Leaving aside any other server vendors, I need some direction as to which 4-way server to buy from HP. HP ProLiant DL580G3s would allow me to standardise but the newer HP ProLiant DL580G4s are more powerful – using the Xeon 71xx chips (formerly codenamed Tulsa) with Intel VT virtualisation support – and, based on list price, are significantly less expensive. Meanwhile, HP’s website claims that ProLiant DL585s are “the best performing x86 4-processor server in the industry” and they cost slightly less than a comparably-specified DL580G4 (again, based on list price), even before taking into account their lower power consumption.

Speaking to Intel, they (somewhat arrogantly) disregarded any reason why I should chose AMD; however AMD were more rational, explaining that regardless of the latest Intel benchmarks, an Opteron is technologically superior for a two main reasons: the hypertransport connection between processor cores; and the integrated memory controller (cf. Intel’s approach of using large volumes of level 3 cache), although the current generation of Opterons only use DDR RAM. Crucially though, AMD’s next-generation dual-core Opterons are socket-compatible with the forthcoming quad-core CPUs (socket F) and are in the same thermal envelope – allowing for processor upgrades – as well as using DDR2 memory and providing AMD-V virtualisation support (but in any case I’ll need to wait a few months for the HP ProLiant DL585G2 before I can buy a socket F-based Opteron 8xxx rack server from HP).

As my virtualisation platform is based on VMware products, I asked VMware which processor architecture they have found to be most performant (especially as the Opteron 8xx does not provide hardware support for virtualisation; although there are doubts about whether ESX Server 3.0 is ready to use such technology – I have read some reports that there will be an upgrade later). Unsurprisingly, VMware are sitting on the fence and will not favour one processor vendor over another (both AMD and Intel are valued business partners for VMware); of course, such comparisons would be subjective anyway but I need to know that I’m making the right purchasing decision. So I asked HP. Again, no-one will give me a written opinion but two HP representatives have expressed similar views verbally – AMD is still in the lead for 4-way servers, at least for the next few months.

There are other considerations too – DL580s feature redundant RAM (after power and disk, memory is the next most likely component to fail and whilst ECC can guard against single-bit failures, double-bit failures are harder to manage); however because the memory controller is integrated in each CPU for an AMD Opteron, there is no redundant RAM for a DL585.

Another consideration is the application load – even virtualised CPUs are perform differently under different workloads: for heavily cached applications (e.g. Microsoft SQL Server or SAP), an Intel architecture may provide the best performance; meanwhile CPU and memory-intensive tasks (e.g. Microsoft Exchange) are more suited to an AMD architecture.

So it seems that it really is “horses for courses” – maybe a split resource pool is the answer with one pool for heavily cached applications and another for CPU and memory-intensive applications. What I really hope is that I don’t regret the decision to follow the AMD path in a few months time… they used to say that “nobody ever got fired for buying IBM“. These days it seems to be the same story for buying Intel.

4 thoughts on “A tale of two CPU architectures

  1. The only Intel announcement that I can find for yesterday relates to vPro. The vPro initiative seems to be centred around Core 2 Duo (i.e. not Xeon server chips), so 4-way Intel systems will still use Xeon 71xx processors (formerly codenamed Tulsa) – an updated version of the previous chip generation (formerly codenamed Paxville MP). Quad-core Xeon chips (codenamed Clovertown) are expected early in 2007 – effectively two Xeon 51xx Woodcrest dies on a multicore module.

  2. from what we have seen in testing – the AMD based 585’s are performing much better than the intel equivalents. hope everything is good – Cheers for now Matt Batchelor

  3. Another indication that AMD is currently outperforming Intel in the 4-way server space is HP’s decision to launch a new ProLiant BL685c server next week but there are no plans for a BL680c Intel equivalent at this time.

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