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Virtualization and InfiniBand

Virtualization and InfiniBand

Posted Aug 29, 2009 12:18 UTC (Sat) by abacus (guest, #49001)
In reply to: Virtualization and InfiniBand by abacus
Parent article: AlacrityVM

Note: there are already kernel drivers in the Linux kernel that use this concept for communication between a virtual machine and the hypervisor or another virtual machine. These drivers are ibmvscsi (initiator, runs in the virtual machine) and ibmvstgt (target, runs in the entity exporting the SCSI device). See also Virtual SCSI adapters for more information.


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Virtualization and InfiniBand

Posted Aug 29, 2009 17:13 UTC (Sat) by giraffedata (subscriber, #1954) [Link]

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.

Virtualization and InfiniBand

Posted Sep 2, 2009 8:02 UTC (Wed) by xoddam (subscriber, #2322) [Link]

Wish *I* got a System P processor standard with *my* virtual machine!


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