The xCloud and Design Alternatives

The xCloud and Design Alternatives

Presented by Lavone Rodolph

OverviewDefinition of VirtualizationWhy Virtualization is hotTwo major virtualization hypervisor platformsCloud ProvidersMajor cloud provider problem for cloud usersSolutions to problemTesting 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 underutilizedData Centers run out of spaceEnergy Cost is highSystem administration cost mounts

Two Major Virtualization VMM Platforms

XenKVM

Xen Hypervisor Platform2 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 ProvidersAmazon (EC2)GoogleIBMMicrosoftRackspaceSalesforce

Cloud Provider ProblemsImmutable 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 AlternativesThe Extensible Hypervisor Design

Download custom extensions (grafts or modules) into hypervisor.

The ExoHypervisor DesignExpose HW through the hypervisor via custom

VMMLibrariesThe 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 1Below 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/OTesting 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).

6. http://searchservervirtualization.techtarget.com/definition/virtualization