1. Manageability, Availability and Performance in Porcupine: A Highly Scalable, Cluster-based Mail Service Yasushi Saito, Brian N Bershad and Henry M.Levy University of Washington

2. Kalyan Boggavarapu Lehigh University CSE 498 What is Porcupine?  Highly scalable Mail server  “Cluster based internet mail server using SMTP”  Why do we need a another mail service ? Conventional systems do not exploit the Heterogeneity of the nodes. Conventional systems are not efficient Conventional systems use legacy software

3. Kalyan Boggavarapu Lehigh University CSE 498 Disadvantages of Conventional Mail Servers  Manageability: The earlier systems are to be configured manually. System has to be tuned for the newly added node / system in the distributed file system. So a lot of work is involved when a node fails or a new node is added to the system.  Availability: This depends on how can the system tolerate the loss of a node. The conventional systems are less fault tolerant When a node has failed the users on that node cannot access the nodes temporarily.  Performance: Number of nodes in the system is not proportional to performance. No dynamic load balancing

4. Kalyan Boggavarapu Lehigh University CSE 498 Goals  Manageability  Availability  Performance Billions messages per second

5. Kalyan Boggavarapu Lehigh University CSE 498 System Overview

6. Kalyan Boggavarapu Lehigh University CSE 498 How Porcupine Achieve its goals

7. Kalyan Boggavarapu Lehigh University CSE 498 Key Data Structures  Mailbox fragment  Mail map  User profile database  User profile soft state (set of users)  User map  Cluster membership list

8. Kalyan Boggavarapu Lehigh University CSE 498 Data Structure Managers

9. Kalyan Boggavarapu Lehigh University CSE 498 A cluster of 2

10. Kalyan Boggavarapu Lehigh University CSE 498 Receiving a Message

11. Kalyan Boggavarapu Lehigh University CSE 498 Load Balancing  Equal distribution of data among the nodes  Identify the hot-spots and divide the load accordingly  Test Bed Systems: 30 Ethernet: 100Mbps OS: Linux 2.2.7 Mean Message Size: 4.7KB; Max 1MB Number of users: 5M Authentication: No

12. Kalyan Boggavarapu Lehigh University CSE 498 Manageability

13. Kalyan Boggavarapu Lehigh University CSE 498 Porcupine re-configures automatically Without: fall in #msgs = 100(approx) With: fall in # of msgs = 50(approx)

14. Kalyan Boggavarapu Lehigh University CSE 498 Availability

15. Kalyan Boggavarapu Lehigh University CSE 498 Mail map consistency  C fails before update  No problem the message is replicated  C deleted all the messages of Bob (A), but update failed.  No problem A will delete the dangling pointers  A fails before the update  A new manager will take the update later

16. Kalyan Boggavarapu Lehigh University CSE 498 States of Replication  Hard State Password and Userlogin is written permanently. Data that should not be lost.  Soft State User to nodes mapping. This can be reconstructed after a loss.

17. Kalyan Boggavarapu Lehigh University CSE 498 Hard State Replication  Aim: consistency  Type: Per- message, Per-User  Effect: efficient during normal operation

18. Kalyan Boggavarapu Lehigh University CSE 498 Effect of Replication

19. Kalyan Boggavarapu Lehigh University CSE 498 Soft-state Reconstruction BCABABAC bob : {A,C} joe : {C} BCABABAC BAABABAB bob : {A,C} joe : {C} BAABABAB ACACACAC bob : {A,C} joe : {C} ACACACAC suzy : {A,B} ann : {B} 1. Membership protocol Usermap recomputation 2. Distributed disk scan suzy : ann : Timeline A B ann : {B} BCABABAC suzy : {A,B} C ann : {B} BCABABAC suzy : {A,B} ann : {B} BCABABAC suzy : {A,B}

20. Kalyan Boggavarapu Lehigh University CSE 498 Advantages of Porcupine  Best use of Resources  Self configuration  Dynamic load balancing  Result: Geographically distributed clusters servers Highly scalable Fault tolerant  Future work Better membership protocol Applying porcupine to other applications like Usenet.

21. Kalyan Boggavarapu Lehigh University CSE 498 Sources  Porcupine figure in all slides is from http://www.bluebison.net/yosemite/porcupine. htm  Diagrams in slides 17,19 are from slides at http://www.hpl.hp.com/personal/Yasushi_S aito/pubs.html#publications