A Closer Look at the Server Node

We’ve arrived at the heart of the server node: the SoC. Calxeda licensed ARM IP and built its own SoC around it, dubbed the Calxeda EnergyCore ECX-1000 SoC. This version is produced by TSMC at 40nm and runs at 1.1GHz to 1.4GHz.

Let’s start with a familiar block on the SoC (black): the external I/O controller. The chip has a SATA 2.0 controller capable of 3Gb/s, a General Purpose Media Controller (GPMC) providing SD and eMMC access, a PCIe controller, and an Ethernet controller providing up to 10Gbit speeds. PCIe connectivity cannot be used in this system, but Calxeda can make custom designs of the "motherboard" to let customers attach PCIe cards if requested.

Another component we have to introduce before arriving at the actual processor is the EnergyCore Management Engine (ECME). This is an SoC in its own right, not unlike a BMC you’d find in conventional servers. The ECME, powered by a Cortex-M3, provides firmware management, sensor readouts and controls the processor. In true BMC fashion, it can be controlled via an IPMI command set, currently implemented in Calxeda’s own version of ipmitool. If you want to shell into a node, you can use the ECME's Serial-over-LAN feature, yet it does not provide any KVM-like environment; there simply is no (mouse-controlled) graphical interface.

The Processor Complex

Having four 32-bit Cortex-A9 cores, each with 32 KB instruction and 32 KB data L1 per-core caches, the processor block is somewhat similar to what we find inside modern smarphones. One difference is that this SoC contains a 4MB ECC enabled L2 cache, while most smartphone SoCs have a 1MB L2 cache.

These four Cortex-A9 cores operate between 1.1GHz and 1.4GHz, with NEON extensions for optimized SIMD processing, a dedicated FPU, and “TrustZone” technology, comparable to the NX/XD extension from x86 CPUs. The Cortex-A9 can decode two instructions per clock and dispatch up to four. This compares well with the Atom (2/2) but of course is nowhere near the current Xeon "Sandy Bridge" E5 (4/5 decode, 6 issue). But the real kicker for this SoC is its power usage, which Calxeda claims to be as low as 5W for the whole server node under load at 1.1GHz and only 0.5W when idling.

The Fabric

The last block in the Soc is the EC Fabric Switch. The EC Fabric switch is an 8X8 crossbar switch that links to five XAUI ports. These external links are used to connect to the rest of the fabric (adjacent server nodes and the SFPs) or to connect SATA 2 ports. The OS on top of server nodes sees two 10Gbit Ethernet interfaces.

As Calxeda advertises their offerings with scaling out as one of the major features, they have created fast and high volume links between each node. The fabric has a number of link topology options and specific optimizations to provide speed when needed or save power when the application does not need high bandwidth. For example, the links of the fabric can be set to operate at 1, 2.5, 5 and 10Gb/s.

A big plus for their approach is that you do not need expensive 10Gbit top-of-rack switches linking up each node; instead you just need to plug in a cable between two boxes making the fabric span across. Please note that this is not the same as in virtualized switches, where the CPU is busy handling the layer-2 traffic; the fabric switch is actually a physical, distributed layer-2 switch that operates completely autonomously—the CPU complex doesn’t need to be powered on for the switch to work.

It's a Cluster, Not a Server Software Support & The ARM Server CPU
Comments Locked


View All Comments

  • JohanAnandtech - Wednesday, March 13, 2013 - link

  • SunLord - Wednesday, March 13, 2013 - link

    Hmm if these didn't cost $20,000 they would make a nice front end for larger websites and forums using less rack space and power. What setup using these would you use for anandtech? Would you guys keep the intel DB server?
  • Gunbuster - Wednesday, March 13, 2013 - link

    I just got a Dell R720xd decked out with 384GB and 4.3TB of storage for a hair over that price.
  • JohanAnandtech - Wednesday, March 13, 2013 - link

    Intel Xeons are still by far a better choice for relational databases that are very hard to split up (sharding is only a last resort)
  • zachj - Wednesday, March 13, 2013 - link

    I'm not sure I agree with the absolutism that seems imlicit in your comment that Xeons are better for relational databases...I think there are cases where that won't be true.

    Database scale-out doesn't always require sharding...using any of a number of different off-the-shelf capabilities built right into most SQL engines, you can create multiple active replicas of your database. This is generally better-suited to workloads that aren't write-intensive, but both clustering and replication allow for writes. While this may seem like a quick-and-dirty solution that is architecturally "less good" than sharding, hardware is a lot cheaper than paying people to design a sharding solution and the dollars very often drive the conversation. As long as the database size isn't terribly large this can be a very cost-effective way to scale out a database.

    I would wager that the Anandtech website database (not the forum database) would probably be well-suited to this type of scale-out. You do waste some money on redundant storage but you more than make up for that cost by not having to pay a development team to implement sharding. If the comments section of the Anandtech website gets stored in the same underlying database, the size constraints and the write activity may appear to be incompatible with this approach, but I would in fact argue that comments don't require relational capabilities of SQL and would be more rightly stored as blobs in Hadoop or Azure Storage Tables. Then the Anandtech database is strictly articles and is both much more compact and almost entirely read-only (except for a few new articles per day).
  • rwei - Friday, March 15, 2013 - link

    To the best of my understanding, replication does well for scaling reads but doesn't do much for writes. I'd still imagine that this would work decently well with AnandTech, where I can't see the volume of writes being that large relative to the volume of reads.
  • Kurge - Wednesday, March 13, 2013 - link

    They would make a horrible front end for such websites. Just buy a single Xeon server and don't artificially limit it by using 24 VMs. Just run the app straight on the metal and it will perform massively better.
  • Oldboy1948 - Wednesday, March 13, 2013 - link

    Very interesting Johan as your tests often are!
    Interesting that the memory bw is so much lower than anything from Intel. In fact Iphone 5 looks much better...why? Only Intel has about the same rsults in compress and decompress.
  • JohanAnandtech - Wednesday, March 13, 2013 - link

    Where did you see the stream results on the A6? I might have missed it somewhere. The only ones I could find reported only 1 GB/s in Triad. http://www.anandtech.com/show/6298/analyzing-iphon... The Quad ECX-1000 got 1.8 GB/s
  • PCTC2 - Wednesday, March 13, 2013 - link

    Do you know what would be an interesting concept for a future version of these cluster-in-a-box systems? A solution like ScaleMP. ScaleMP is basically a reverse VM. A hypervisor on each server clusters together to run a single OS with an aggregation of all resources (cores, RAM, network, and disk). ScaleMP running on 4x Dual-socket 8-core Xeon systems w/ 32GB RAM results in a usable system with 64-cores and 128GB RAM as if it was running natively on the hardware. This would be an interesting concept to transfer to the ARM space (if a form of hardware virtualization ever is designed). In a box like this, there would be 192 cores and 192GB of RAM available to a single Fedora instance. Cluster 2 of these together and suddenly there's a system with 384 cores and 384GB of RAM in 4U. Just some food for thought.

Log in

Don't have an account? Sign up now