Netbus: A Transparent Mechanism for Remote Device Access in Virtualized Systems Sanjay Kumar PhD Student Advisor: Prof. Karsten Schwan

Remote Device Access Transparent access to remote devices is becoming essential in various computing environments –datacenters, clusters and even in personal computing –Remote disks, backup drives, movie on a thin client etc. Essential in virtualized environment for VM migration –Easy for networked devices iSCSI, NAS, SAN But what about non-networked devices? –NDB, DRBD etc. for block devices No support during VM migration Netbus: Provides transparent and generic access to remote devices –Virtual device migration and device hot-swapping

Networ k Backup DVD-drive IPod on networked docking station Blade-Server

Netbus Software Architecture Targets high-bandwidth, low-latency and reliable networks with single administrative domain –Datacenters, blade-servers, clusters, home and office LAN Similar to channels in pub/sub systems –Server exports the device (channel), Client connects (subscribe) to it Logical extension of frontend-backend approach to device virtualization –Frontend can communicate with a remote backend –Application layer client establishes the connection with server The fast path is inside kernel –Abstraction of a network bus Generic mechanism with device specific callback functions –Common Netbus header followed by device specific data –Data passed to device specific callbacks for further processing

Netbus: Software Architecture (contd.) Hypervisor Service VM Service VM Hypervisor Guest VM L-BE FE vdevice device R-BE device driver Local Machine Remote Machine Netbus Network Client Add remote Dev. to VM Server Hypervisor Service VM Guest VM BE FE vdevice device driver Local Machine Add Device to VM device User Kernel

Netbus: Software Architecture (contd.) Virtual Device Migration –Migrate virtual devices along with VMs –Provides continuous access to VMs devices after VM migration through Netbus –How to deal with pending I/O operations? Bring the device into a quiescent state before migration –No pending I/O operations –I/O operations get queued into the FE and complete after VM migration

Hypervisor Service VM Service VM Hypervisor Guest VM L-BE FE vdevice device R-BE device driver Local Machine Remote Machine Netbus Network Client Add remote Dev. to VM Server User Kernel Guest VM FE device driver vdevice VM Migration Virtual Device Migration and Device Hot-swapping device

Netbus: Software Architecture (contd.) Device Hot-swapping –Replace the remote device with an equivalent local device while in operation –Increases throughput, removes network dependence, hardware maintenance – Useful for rarely migrated VMs –How to deal with pending IO operations Same as with virtual device migration –Can be combined with virtual device migration To complete both operations in one shot Netbus prototype implemented in Xen and works for block and USB devices

Netbus Evaluation Testbed description –Two Dell Poweredge 2650s connected through a gigabit switch –Each machine has GHz, 2-wat HT Xeon CPUs and 2 GB RAM –Iozone file I/O benchmarks used Write throughput of block devices

Write throughput of block devices without buffer caching

Netbus Latency Latency incurred by various components in accessing IO devices

Virtual Device Migration MySQL server migration in RuBIS online auction benchmark

RuBIS Database server VM migration Effect on RUBiS Throughput due to MySQL Server Migration

Effect on Iozone throughput due to VM migration and disk hot-swapping

Questions??

Remote Device Sharing Host1 Host3 Host4 Host2 device1 device3 device2 device4 vdevice4 vdevice2 vdevice4