Cloud Computing is gaining momentum as one of the technologies that promises to subvert our own idea of computing. With an increasing usage of cloud applications and their consequent dependency from connectivity, the nowadays Personal Computer is becoming merely a mobile device acting as a front-end to on-line applications and services. This huge paradigm shift in computing is witnessed for example by big market players who announced the imminent launch of innovative products and Operating Systems (like Chrome notebooks and the accompanying Chrome OS2. by Google), which are capable of projecting the user into the network in a few seconds by booting and starting immediately a web browser and (mostly) nothing else. In such a challenging scenario, more and more of the applications that we traditionally used locally on our PC are being hosted on cloud infrastructures and operated remotely through the Internet. This includes not only batch tasks, but also interactive applications which need to operate inherently with good levels of responsiveness. In this paper, the challenging problem is discussed of how to ensure predictable levels of Quality of Service (QoS) to cloud applications across the multiple layers of a typical cloud infrastructure, and how a reasonable Service Level Agreement (SLA) management and enforcement policy might look like. The scope of this paper represents a hands-on experience that was gained by the authors realising the IRMOS real-time cloud-computing infrastructure in the context of the IRMOS European Project

1. SLAs in Virtualized Cloud Computing
Infrastructures with QoS Assurance
Tommaso Cucinotta G. Gogouvitis, K. Kostanteli
Scuola Superiore Sant'Anna National Technical University of Athens
Italy Greece
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

2. Motivations & background
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

3. Introduction
Towards a new computing paradigm
●
Computing, network, storage in the cloud
●
Not only batch computing and storage
●
but also interactive real-time applications
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

4. Virtualization
Virtualization is a key technology
For IaaS providers (Cloud Computing)
Enables server consolidation
Physical Host
Physical Host
OS
OS
...
Physical Host
Physical Host
OS
OS
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

5. Virtualization
Virtualization is a key technology
For IaaS providers (Cloud Computing)
Enables server consolidation
Physical Host
Physical Host Physical Host
Physical Host
OS
OS VM/OS
VM/OS
... ...
Physical Host VM/OS
VM/OS
Physical Host
OS
OS
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

6. Need for Performance Isolation
Resource sharing
→ Temporal interference
Physical Host
Physical Host
VM
VM
VM
VM
VM
VM
VM
VM
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

7. Need for Performance Isolation
Resource sharing ~30ms
VM Alone
→ Temporal interference
Physical Host
Physical Host
VM
VM
VM
VM
VM
VM
VM
VM
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

8. Need for Performance Isolation
Resource sharing ~30ms
VM Alone
→ Temporal interference
Physical Host
Physical Host
VM
VM
VM
VM τ1 = (30ms, 150ms)
τ2 = (50ms, 200ms)
~120ms
VM
VM 2 VMs
VM
VM
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

9. Need for Performance Isolation
Resource sharing How it looks like when you buy
→ Temporal interference
Physical Host
Physical Host
VM
VM
VM
VM
VM
VM
VM
VM
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

10. Need for Performance Isolation
Resource sharing How it looks like when you buy
→ Temporal interference
Physical Host
Physical Host
VM
VM
VM
VM
How it looks like when you use
VM
VM
VM
VM
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

11. Possible Solutions
Hardware replication and
static partitioning Physical Host
Physical Host
Computing VM
VM
• Multi-core (1 core per VM)
• NUMA awareness
VM
VM
Networking
• Multiple network adapters
(1 network adapter per VM)
VM
VM
• Multi-queue adapters
Drawbacks
VM
VM
Limitation of flexibility
Under-utilization of resources
• e.g., with real-time/interactive workloads (cloud computing)
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

12. Possible Solutions
Another approach
• Let multiple VMs use the same resources
• Use proper resource scheduling strategies
For example
• Computing
• Xen credit-based and SEDF schedulers
• Networking
• QoS-aware protocols (IntServ, MPLS, WF2Q+)
Advantages
• Increased flexibility
• Increased resource saturation levels
• Reduced infrastructure costs
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

13. Objectives: Resource Sharing in Distributed
Applications with RT Constraints
Optimum/reasonable deployment of VSNs on PNs
Given computing/network/memory requirements
Respecting end-to-end timing constraints Physical Host
Physical Host
Computing/Memory Networking
Requirements Requirements Physical
Subnet
Physical
Link
Physical Host
Virtual Service Network
Maximum response-time Physical Host
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

14. The IRMOS Approach
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

15. IRMOS
Focus: Interactive Real-time Multimedia
on SOIs
Application Scenarios
SaaS
Framework Services
PaaS
Intelligent Service-Oriented
Networking Infrastructure
IaaS (ISONI)
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

16. The IRMOS Vision
A Service Oriented Infrastructure, which allows the adoption of
interactive real-time applications
We faced with a set of challenges:
Enabling real-time attributes at various levels of the infrastructure (network,
storage, processing, application, business)
QoS Guarantees
Automated SLA Negotiation
Mapping between high-level application terms and fine-grained resource-level
attributes
Specification Languages to describe real-time applications
...
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

17. IRMOS Two-Phase Approach
Design
Tools
Benchmarking Application
Concretion Discovery
Negotiation
Mechanisms for
Mechanisms for Reservation
Modeling,
Methodology for the
Methodology for the
Analysis, precise allocation of
precise allocation of
Planning identification of
identification of resources
resources Service
resource requirements
resource requirements to applications Instantiation
to applications
Service
Component
Configuration
Execution &
Monitoring
Cleanup
Offline
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

18. IRMOS Two-Phase Approach
Design
Tools
Benchmarking Application
Concretion Discovery
Negotiation
Modeling, Reservation
Analysis,
Planning
Service
Instantiation
Service
Component
Configuration
Execution &
Monitoring
Cleanup
Offline
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

19. Demonstrators
Collaborative Digital Film Post-production
Virtual and Augmented Reality
Interactive collaborative e-learning
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

20. Challenging Issues
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

21. Cloud Players: Different Views & Interests
The Customer
Minimum costs
Proper/acceptable performance
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

22. Cloud Players: Different Views & Interests
The Customer
Minimum costs
Proper/acceptable performance
The User
Maximum performance
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

23. Cloud Players: Different Views & Interests
The Customer
Minimum costs
Proper/acceptable performance
The User
Maximum performance
The IaaS Provider
Maximum revenues, minimum costs
Maximum consolidation levels
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

24. Cloud Players: Different Views & Interests
?
The Customer
Minimum costs
Proper/acceptable performance
The User
Maximum performance
The IaaS Provider
Maximum revenues, minimum costs
Maximum consolidation levels
Agreement ?
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

25. *aaS Provisioning and Risks
IaaS Provider
May rent physical resources (e.g., 1 GHz AMD for 1 year)
• Easy, low risk
May rent computing power (e.g., 10 GFLOPS for 1 year)
• More difficult
SaaS Provider
QoS parameters in the domain of applications (e.g., fps)
• Very difficult, high risk
• Requires performance stability, models & prediction
Adaptation is key
• Monitoring
• Feedback Loops
• Scalability
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

26. Predicting Applications Performance
Performance Prediction
●
Benchmarking/Profiling (via Monitoring)
●
Stochastic Models
●
Neural Networks (black-box approach)
●
Temporal isolation for computing & data flows makes the job
easier
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

27. Future Research
How to formally specify QoS requirements in SLAs ?
●
So that the offered and provided QoS is verifiable by parties ?
●
What is the observation window over which the levels of QoS
should be granted/verified ?
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

28. Future Research
How to formally specify QoS requirements in SLAs ?
●
So that the offered and provided QoS is verifiable by parties ?
●
What is the observation window over which the levels of QoS
should be granted/verified ?
How to solve disputes among parties ?
●
Certification ?
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

29. Future Research
What business models may account for
Imprecise QoS guarantees
Probabilistic QoS/availability guarantees
Pay-back penalties in case of SLA violation
?
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

30. References
T. Cucinotta, K. Konstanteli, T. Varvarigou, "Advance Reservations for Distributed Real-
TimeWorkflows with Probabilistic Service Guarantees", IEEE International Conference on Service-
Oriented Computing and Applications (SOCA 2009), December 2009, Taipei, Taiwan
K. Kostanteli, D. Kyriazis, T. Varvarigou, T. Cucinotta, G. Anastasi, "Real-time guarantees in
flexible advance reservations", 2nd IEEE International Workshop on Real-Time Service-Oriented
Architecture and Applications (RTSOAA 2009), Seattle, Washington, July 2009
F. Checconi, T. Cucinotta, D. Faggioli, G. Lipari, "Hierarchical Multiprocessor CPU Reservations for
the Linux Kernel", in 5th International Workshop on Operating Systems Platforms for Embedded
Real-Time Applications (OSPERT 2009), Dublin, Ireland, June 2009
T. Cucinotta, G. Anastasi, L. Abeni, "Real-Time Virtual Machines", in 29th Real-Time System
Symposium (RTSS 2008) -- Work in Progress Session, Barcelona, December 2008
YouTube Video on e-Learning performance isolation:
http://www.youtube.com/watch?v=8FbHZ4ytNoQ
IRMOS YouTube channel:
http://www.youtube.com/user/irmosproject
IRMOS Project Website: http://www.irmosproject.eu
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna

31. Thanks for your attention
Questions ?
Workshop “eContracting in the Clouds” – Oct 26th 2011 – Tommaso Cucinotta – Real-Time Systems Laboratory – Copyright 2011 Scuola Superiore Sant'Anna