The xCloud and Design Alternatives Presented by Lavone Rodolph

Overview Definition of Virtualization Why Virtualization is hot Two major virtualization hypervisor platforms Cloud Providers Major cloud provider problem for cloud users Solutions to problem Testing Results

Virtualization Definition “Virtualization is the creation of a virtual device or resource such as a server, storage device, network or even an operating system” [3]

Why virtualization is hot The 4 drivers of virtualization Hardware is underutilized Data Centers run out of space Energy Cost is high System administration cost mounts

Two Major Virtualization VMM Platforms Xen KVM

Xen Hypervisor Platform 2 Main Components: Hypervisor (VMM) – manages memory, CPU scheduling, etc. VM0 (Domain 0) – has direct access to HW. Provides device drivers and I/O mgmt. for guest VM’s Paravirtualization replaces all privileged instructions with direct calls to hypervisor

KVM Hypervisor 4 privilege levels Rings 0-3 Ring 0 (Most Privileged) controls HW& Sys. Functions KVM model depends on architecture set. Ex. In X86 Guest OS runs in Ring 3, Rings 1 & 2 not used.

Cloud Providers Amazon (EC2) Google IBM Microsoft Rackspace Salesforce

Cloud Provider Problems Immutable Hypervisor and Buried HW Users are dependent on Cloud Vendor hypervisor tools Ex.) Amazon EC2 – CloudWatch Monitoring tool, Elastic load balancing. Users can not create custom hypervisor tools or employ techniques (such as efficient page sharing) at the hypervisor level. HW details lies behind virtual abstraction. Users can only use HW interfaces exposed by cloud provider

Solution: General Extensibility Architecture Note: U = User modules, P = Provider modules Allows user to create custom hypervisor modules. Interact directly with provider modules and with HW. Provide better service, enhanced performance Note: Provider Modules multiplex HW & enforce protection (isolate containers)

Three Design Alternatives The Extensible Hypervisor Design Download custom extensions (grafts or modules) into hypervisor. The ExoHypervisor Design Expose HW through the hypervisor via custom VMMLibraries The Nested virtualization approach Add another Virtual Machine Monitor (Hypervisor) that user can control

The Extensible Hypervisor Design Allows user to have some control of the hypervisor by downloading custom modules/extensions into the kernel Based on extensible OS ex. (SPIN & VINO) User defined modules make hypervisor mutable Modules execute in privilege mode, can access HW

The Extensible Hypervisor Design Immutable modules must be protected. Safe languages (ex. Modual- 3) are used to protect immutable modules Software fault isolation protect modules

The ExoHypervisor Design VMMlibrary used to manage HW, instead of Kernel, kernel enforces protection between applications VMMLibrary can be custom built Library can be linked to application Allows users to access HW Based on Exokernel OS LibVMM is mutable

Nested Virtualization Approach User modules made in the user controlled VM HW still remains buried However, paravirtualization may be applied Provider involvement is not necessary

Testing Nested Virtualization Design Nested virtualization testing performed within Amazon EC2 on machines with 24GB of RAM, 6 dual core 2.3GHz Intel Xeon X5670 Processors.

Testing Results 1 Below are microbenchmark testing results using lmbench for performing the following operations: double division, null system calls and fork. PV invokes hypervisor on system call. PV Fork causes overhead by inducing traps in lower layer hypervisor (it’s not privileged to do so)

Testing Disk I/O Testing I/O by writing 1.6 GB of data to a disk partition using blocks of size 256K. Tested 5 times Results: Nested virtualization did not cost much overhead, it achieved 90% throughput

I/O Results

References 1. ELDEHIRY, M., ELNIKETY, E., HUANG, H., JAMJOOM, H,. WEATHERSPOON, H., AND WILLIAMS, D. Unshackle the Cloud! In Proc. of USENIX HotCloud’11 (Portland, OR, June 2011). 2. BARHAM, P., DRAGOVIC, B., FRASER, K., HAND, S., HARRIS, T., HO, A., NEUGEBAUER, R., PRATT, I., AND WARFIELD, A. Xen and the art of virtualization. In Proc. of ACM SOSP (Bolton Landing, NY, Oct. 2003). 3. BEN-YEHUDA, M., DAY, M. D., DUBITZKY, Z., FACTOR, M., HAR’EL, N., GORDON, A., LIGUORI, A., WASSERMAN, O., AND YASSOUR, B.- A. The turtles project: Design and implementation of nested virtualization. In Proc. of USENIX OSDI (Vancouver, BC, Canada, Oct. 2010).

References (cont.) 4. BERSHAD, B. N., SAVAGE, S., PARDYAK, P., SIRER, E. G., FIUCZYN- SKI, M. E., BECKER, D., CHAMBERS, C., AND EGGERS, S. Extensibil- ity, safety and performance in the SPIN operating system. In Proc. of ACM SOSP (Copper Mountain, CO, Dec. 1995). 5. CLARK, C., FRASER, K., HAND, S., HANSEN, J. G., JUL, E., LIMPACH, C., PRATT, I., AND WARFIELD, A. Live migration of virtual machines. In Proc. of USENIX NSDI (Boston, MA, May 2005) virtualization