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LWN.net Weekly Edition for May 23, 2013
An "enum" for Python 3
An unexpected perf feature
LWN.net Weekly Edition for May 16, 2013
A look at the PyPy 2.0 release
10G ethernet isn't low latencies at all costs. it benifits/suffers from backwards compatibility issues.
it also allows for longer cable runs than IB
it's not that one is alwaysbetter than the other, it's that each has it's use
if you are wiring a cluster of computers and price is not an issue, then IB clearly wins
if you are wiring a building, than IB _can't_ do the job, but 10G Ethernet can, so it clearly wins
Virtualization and InfiniBand
Posted Aug 8, 2009 11:00 UTC (Sat) by abacus (guest, #49001)
Posted Aug 29, 2009 12:18 UTC (Sat) by abacus (guest, #49001)
Posted Aug 29, 2009 17:13 UTC (Sat) by giraffedata (subscriber, #1954)
You've given an example I actually know something about, so I can comment further. You're talking about the mechanism used on IBM's System P processors (which come standard with virtual machines) to allow a server in virtual machine S to present a SCSI disk device to client virtual machine C.
The server in S bases its disk devices on real SCSI disk devices (e.g. it splits a 10G real SCSI disk into 5 2G disks, one for each of 5 client virtual machines), and the actual data transfer is conventional DMA done by the real SCSI HBA to the memory of C, using hypervisor facilities specifically designed for this I/O server VM application.
AFAICS the only infiniband-related part of this is SRP (SCSI RDMA (Remote DMA) Protocol). SRP is how the program running in S initiates (by communicating with C) that DMA into memory C owns, much as a server at the end of an IB cable might set up to transmit data down the IB wire into the client's memory.
And as I recall, SRP is simple and not especially fast or low-latency -- just what anybody would design if he needed to communicate DMA parameters. A person could be forgiven for just reinventing SRP for a particular application instead of learning SRP and reusing SRP code.
Posted Sep 2, 2009 8:02 UTC (Wed) by xoddam (subscriber, #2322)
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