Data access in HPC infrastructures is realized via user-level networking and OS-bypass techniques through which nodes can communicate with high bandwidth and low-latency. Virtualizing physical components requires hardware-aided software hypervisors to control I/O device access. As a result, line-rate bandwidth or lower latency message exchange over 10GbE interconnects hosted in Cloud Computing infrastructures can only be achieved by alleviating software overheads imposed by the Virtualization abstraction layers, namely the VMM and the driver domains which hold direct access to I/O devices.In this paper, we present MyriXen, a framework in which Virtual Machines efficiently share network I/O devices bypassing overheads imposed by the VMM or the driver domains. MyriXen permits VMs to optimally exchange messages with the network via a high performance NIC, leaving security and isolation issues to the Virtualization layers. Smart Myri-10G NICs provide hardware abstractions that facilitate the integration of the MX semantics in the Xen split driver model. With MyriXen, multiple VMs exchange messages using the MX message passing protocol over Myri-10G interfaces as if the NIC was assigned solely to them. We believe that MyriXen can integrate message passing based applications in clusters of VMs provided by Cloud Computing infrastructures with near-native performance.
We present gmblock, a block-level storage sharing system over Myrinet which uses an optimized I/O path to transfer data directly between the storage medium and the network, bypassing the host CPU and main memory bus of the storage server. It is device driver independent and retains the protection and isolation features of the OS. We evaluate the performance of a prototype gmblock server and find that: (a) the proposed techniques eliminate memory and peripheral bus contention, increasing remote I/O bandwidth significantly, in the order of 20-200% compared to an RDMAbased approach, (b) the impact of remote I/O to local computation becomes negligible, (c) the performance characteristics of RAID storage combined with limited NIC resources reduce performance. We introduce synchronized send operations to improve the degree of disk to network I/O overlapping. We deploy the OCFS2 shared-disk filesystem over gmblock and show gains for various application benchmarks, provided I/O scheduling can eliminate the disk bottleneck due to concurrent access.
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