Thinking about HPC Infrastructure

by kishi on December 01, 2006 04:21pm

I started the first HPC blog (See “previous blog“) with an understanding that HPC is an area where there has been a surge of activity from a development/investment standpoint. This segment of Information Technology has experienced a heightened level of engagement from OEM’s and partners, all trying to meet the growing computing needs of their customers. So after getting a basic understanding behind the importance of why HPC matters, the next logical step that needed uncovering was “How to think” about HPC Infrastructure and tap into the “wisdom” behind managing it. You might ask why this is relevant. For starters, setting up HPC Infrastructure is an experience that, just like any other infrastructure, be it Network or Storage, requires intricate planning and intimate familiarity with its individual contributing components. In case of HPC, let’s just say you really need to know your nodes J. Let’s talk more about what’s involved in setting up an HPC Infrastructure and how to think about it as a whole:

1.    Investment Impetus: To successfully plan and design an HPC Infrastructure, the first and foremost step should be to “look beneath the surface” . This simply means to understand, the primary reason for investing in HPC. The demand for HPC equipment, linked to a set of business objectives should have clear purpose around the outcome and expectation. This is specially true today than at any other moment in time because the consumption of HPC cycles, specifically in the research and development areas across all verticals has seen a steady 70% growth over the past four years (Source: primeur ). Despite this tremendous growth in the proliferation of HPC technology,  the growth pattern itself is sporadic. One of the reasons for it may be the complexity, not only in terms of design but also in terms of consumption as well.  Take the case of SHARCNET in Southern Ontario that developed a long range plan around adoption and implementation of HPC technology. According to the report, some of the elementary challenges around planning for HPC emerge from the fact that “it is an enabling technology for an extremely diverse set of researchers”. This embodies the essence of the sentiment behind the complexity and diversity predominant in the HPC space.

2.    Planning and Designing Hardware: While thinking about planning and designing an HPC infrastructure implementation, I spoke to several folks in this area, drew from a decade and a half of my experience as an Infrastructure Architect and thought of some key areas that I would consider. These include:

a.  Facility considerations (Rackspace, Power and Cooling): Talk to any enterprise level Datacenter manager what his/her top 10 pain-points are and you are bound to hear the words “rackspace, power and cooling” in what follows. Dig deeper and you’ll realize that in any datacenter, there’s a fixed number of colo’s (Colocation) you can populate based on the HVAC designs. This means that rackspace is what’s at a premium in each of these colo’s with every “u” accounted for. Packing in dense chipsets in small form-factor server add to existing power and cooling challenges

Translation – you need more outlets and more airflow per rack than what you did a decade ago with a handful of 4 and 5u servers taking up the entire rack

b.  Physical Plant planning: Quoting the resident HPC Guru Frank Chism who says “I cannot over emphasize the importance to planning for physical plant in HPC deployments. Things like room and raceways for well managed and planned cabling. HPC uses more cable than anything except maybe SAN. Also, pay attention to floor loads, air flow, clean and redundant power. Finally, never never forget out-of-band management. Deep subfloor really helps with all that cabling”.

Translation – Effective HPC performance calls for an effective HPC design, which includes tweaking hard as well as soft components. These components can be as covert as chip-design or as overt as subfloor depth.

c.  Hardware and Processing Power: Pushing the envelope on hardware and processor architectures today translates to increased performance (the heart and soul of HPC). Adding energy efficient hardware on top of the architecture amounts to greater investment in raw computing power, which in turn translates to building a sound HPC infrastructure. The key advantages one needs to look for in this scenario are faster data access and increased instructions. The word “performance” is repeated throughout the theme of this topic because it IS what HPC is all about, the ability to reduce the number of cycles to process data. Addressing the hardware and processing specs as part of core requirements ensures a smoother build-out.

3.    Implementing HPC Tools and Software: Like any other piece of hardware, a HPC cluster is just that until software and tools exploit the underlying architecture to drive results and performance to do what it does best – compute. When thinking of some core elements of HPC tools and software, here’s how I thought to break them up:

a.  Setup and deployment systems: Setting up HPC clusters goes back to what I said earlier in Section 1 – what do you want to do with it? Although there are various ways and methods that allow you to drive the software and installation experience of an HPC system, the bottom line is that this depends to a great extent of what components make up the genetic composition of the HPC cluster you ordered. Taking a look at some HPC software setup and deployment tools out there, a few mainstream ones are SCALI and HP-MPI (HP’s message passing interface). These packages provide deployment, monitoring and job scheduling services for managing and administering an HPC cluster just like IBM’s CSM (Cluster Systems Manager). In the Open Source space, there’s Maui and Torque, that work as job scheduler and resource managers for managing compute nodes and clusters. Platform Rocks is another suite of utilities that allow installation and integration of third party apps

b.  Parallel FS: This is truly what I think is going to be the frontier for some intense activity over the next few years. Using Wikipedia’s description, “Distributed parallel file systems stripe data over multiple servers for high performance. Some of the distributed parallel file systems use object storage device (OSD) (In Lustre called OST) for chunks of data together with centralized metadata servers such as Ceph Scalable, Distributed File System from University of California, Santa Cruz. (Fault-tolerance in their roadmap.), Lustre from Cluster File Systems. (Lustre has failover, but multi-server RAID1 or RAID5 is still in their roadmap for future versions.) and Parallel Virtual File System (PVFS, PVFS2)”.

Deep-Dive: At Base, parallel file systems are global namespaces for files that achieve high bandwidth via parallelism. That bandwidth comes in three dimensions, high aggregate bandwidth, high single stream bandwidth, and high metadata operations per second. No one seems to have achieved high performance in all of these dimensions. Don’t forget that the volumes of data are so large that backup is a major undertaking and thus, reliability is required as well. Further, nobody seems to be able to make a parallel file system that performance well for high-speed data for short I/Os, like say you do when compiling a major application

c.  Multiple Networks: A final comment on implementation of HPC is that HPC often has multiple networks. For example, it does little good to have a parallel file system that delivers gigabytes per second of data to single nodes if the network can’t handle that much bandwidth!

So in conclusion, here’s a recap on the learning behind setting up HPC Infrastructure:

    • Comprehensive understanding beneath WHY you’re investing in HPC and what you expect as an outcome
    • Deep familiarity with the core HPC Hardware and design components
    • Facility and Physical plant considerations to ensure adequate cabling and subfloor space
    • Visibility into prominent HPC based software and toolsets
    • Understanding the three dimensions of bandwidth
    • And finally accommodating the concept of “Multiple Networks” into node design to accommodate the required bandwidth

Look forward to getting back to you with more on HPC over the new few weeks again. Until then “Happy Computing”!!

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