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The Aurora Project

[Disk QoS Project Logo]
"Enforcing Quality of Service Guarantees in Storage Systems"


With system area networks (SANs) storage resources are being moved from individual hosts to a shared pool, for both ease of administration and economies of scale. This trend is causing many applications to share each storage device. Such contention between applications can cause poor performance, especially when some require timely access to the devices, yet others are more relaxed. Enforcing service level agreements (SLAs), or quality of service (QoS) guarantees to partition resources between applications, and to ensure those that need it have the timely access they require, can ease this tension.

The aim of this project is to develop mechanisms for enforcing such guarantees in the disk drives or disk arrays, and a suitable language for expressing application's requirements to the system. The project may be conducted with the funding of Hewlett-Packard's Storage Systems Program, and will be building upon past work conducted at the University's computer laboratory, in particular the Desk Area Network (DAN), Pegasus and Measure projects.


The project will be conducted over three years, between December 1998 and December 2001, at which point we hope to have achieved:
  • QoS specification suitable for enforcement in storage devices.
  • Policing and enforcement mechanisms for the storage devices.
  • Usage prediction mechanisms to provide statistical, or deterministic, performance guarantees.
The key stages of the project are:
July 1999 
Demonstration of a simple network-attached storage device cable of enforcing simple Quality of Service policing between simultaneous transaction streams.
December 1999 
Evaluation of a QoS-enforcing scheduler when dealing with a range of workloads. Clear identification of the scheduling parameters need to enforce isolation between clients in the storage device.
December 2000 
Show how service level agreements required by applications can be translated into the scheduling parameters that the device operates with.
December 2001 
Exhibit a scalable shared storage system with a basic admission control scheme that can guarantee clients with predictable, yet efficient service.


Ian Pratt
John Wilkes
Dave Stewart
Jean Bacon
Principal Investigator
Research Student
Lecturer and research fellow of King's College, Cambridge UK. Of the Storage Systems Program of Hewlett Packard's Computer Systems Laboratory, Palo Alto, 
Of Churchill College, Cambridge UK.


Some of the related work conducted at the Computer Laboratory: 
The User-Safe Device I/O Architecture (Gzipped Postscript
Ian Pratt, dissertation submitted for the degree of Doctor of Philosophy. 
User-Safe Devices for True End-to-End Qos (Gzipped Postscript
Ian Pratt, published in NOSSDAV '97. 
A Fresh Approach to File System Quality of Service (Text, Gzipped Postscript
Paul Barham, published in NOSSDAV '97. 
The Desk Area Network (Compressed Postscript
Mark Hayter, Derek McAuley, Cambridge University Computer Laboratory Technical Report 228. 
Devices on The DAN (Postscript
Ian Pratt, slides for a talk given to the NISC NASD Working Group. 
Devices in a Multi-Service Operating System (Text, Gzipped Postscript
Paul Barham, Cambridge University Computer Laboratory Technical Report 403.