[Beowulf] Questions about upgrading InfiniBand
prentice at ias.edu
Wed Apr 18 15:02:26 EDT 2012
Aggregation spine? Can you tell me more about that? Can you give me a
On 04/18/2012 11:22 AM, Andrew Howard wrote:
> I would talk to Mellanox about your options for switch topology. We
> opted not to go with the single 648-port FDR director switch, but
> instead use top-of-rack leaf switches (the 36-port guys) and then an
> aggregation spine to connect those. It performs beautifully. It also
> means we don't have to worry about buying longer (more expensive)
> cables to run to the director switch, we can buy the shorter cables to
> run to the rack switch and then only have to buy a few 10M cables to
> run to the spine.
> Andrew Howard
> HPC Systems Engineer
> Purdue University
> (765) 889-2523
> On Wed, Apr 18, 2012 at 11:05 AM, Prentice Bisbal <prentice at ias.edu
> <mailto:prentice at ias.edu>> wrote:
> I'm planning on adding some upgrades to my existing cluster, which has
> 66 compute nodes pluss the head node. Networking consists of a Cisco
> 7012 IB switch with 6 out of 12 line cards installed, giving me a
> capacity of 72 DDR ports, expandable to 144, and two 40-port ethernet
> switches that have only six extra ports between them.
> I'd like to add a Lustre filesystem (over InfiniBand) to my cluster,
> and then begin adding/replacing nodes in the cluster. Obviously, I'll
> need to increase capacity of both my IB and ethernet networks. The
> questions I have are about upgrading my InifiniBand.
> 1. It looks like QLogic is out of the InfiniBand business. Is Mellanox
> the only game in town these days?
> 2. Due to the size of my cluster, it looks like buying a just a
> core/enterprise IB switch with capacity for ~100 ports is the best
> option (I don't expect my cluster to go much bigger than this in the
> next 4-5 years). Based on that criteria, it looks like the Mellanox
> IS5100 is my only option. Am I over looking other options?
> 3. In my searching yesterday, I didn't find any FDR core/enterprise
> switches with > 36 ports, other than the Mellanox SX6536. At 648
> the SX6536is too big for my needs. I've got to be over looking other
> products, right?
> 4. Adding an additional line card to my existing switch looks like it
> will cost me only ~$5,000, and give me the additional capacity
> I'll need
> for the next 1-2 years. I'm thinking it makes sense to do that,
> and wait
> for affordable FDR switches to come out with the port count I'm
> for instead of upgrading to QDR right now, and start buying hardware
> with FDR HCAs in preparation for that. Please feel free to
> agree/disagree. This brings me to my next question...
> 5. FDR and QDR should be backwards compatible with my existing DDR
> hardware, but how exactly does work? If I have, say an FDR switch
> with a
> mixture of FDR, QDR, and DDR HCAs, will the whole fabric slow down to
> the lowest-common denominator, or will the slow-down be based on
> the two
> nodes involved in the communication only? When I googled for an
> all I found were marketing documents that guaranteed backwards
> compatibility, but didn't go to this level of detail, I searched the
> standard spec (v1.2.1), and didn't find an obvious answer to this
> 6. I see some Mellanox docs saying their FDR switches are
> compliant with
> v1.3 of the standard, but the latest version available for download is
> 1.2.1. I take it the final version of 1.3 hasn't been ratified yet. Is
> that correct?
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