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Megastore - ID2220 Presentation
 

Megastore - ID2220 Presentation

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Paper presentation for Advanced Topics in Distributed System. Original paper can be found here -> http://research.google.com/pubs/pub36971.html

Paper presentation for Advanced Topics in Distributed System. Original paper can be found here -> http://research.google.com/pubs/pub36971.html

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    Megastore - ID2220 Presentation Megastore - ID2220 Presentation Presentation Transcript

    • Megastore Providing Scalable, Highly Available Storage for Interactive Services Paper by Jason Barker et al. Presented by Arinto Murdopo arinto@kth.se7/11/2012 1
    • OutlineMotivationMegastore:  Features  Scalability  Availabilty  Putting them all togetherObservationConclusions7/11/2012 2
    • Motivation  Conflicting requirements • RDBMS – easy to use, but not scale • NoSQL – scale, but not easy to use  Interactive online services • Highly available and fast response time7/11/2012 3
    • Here comes Megastore easy to use • ACID semantics scalable • data partitioning highly available • synchronous replication through modified Paxos7/11/2012 4
    • Easy to use - Featurescost-transparent APIs • No API for joins • Joins are implemented in application codedata model • schema, table (entity), property • entity clustering • indexes: local, global • Bigtable column name == Megastore table name and property name, i.e User.name7/11/2012 5
    • Easy to use - Featurestransactions and concurrency control • Bigtable for concurrency control • transaction lifecycle: read, application logic, commit, apply, clean upothers • backup system of transaction logs • encryption7/11/2012 6
    • ScalableScale the replication scheme Data partitioning • Entity group concept Data locality • Entity group locality • Bigtable instances locality7/11/2012 7
    • Entity GroupsEntity is like instance of table.Entity group is group of entities. i.e Email Application • Email account Blog Application • User Profile • Blog post + metadata • Blog unique name7/11/2012 8
    • Entity Groups7/11/2012 9
    • Highly AvailableReplicate mutations of write-ahead log inside entity groupsusing modified Paxos, but let’s revisit original Paxos…7/11/2012 10
    • Modified Paxos – Fast ReadsRead in original Paxos7/11/2012 11
    • Modified Paxos – Fast ReadsContact Coordinator and read locally if possible7/11/2012 12
    • Modified Paxos – Fast WritesSkip “prepare” stage in subsequent write of sameleader, provided no write from other writers7/11/2012 13
    • Modified Paxos – New ReplicaTypes  Full Replicas  all replicas that we have seen until now  Witness Replicas  are able to vote  store but do not apply write-ahead logs  do not store entity data  Read-only Replicas  are not able to vote  snapshots of entity data7/11/2012 14
    • Putting them all togetherMegastore Architecture7/11/2012 15
    • Reads Query Local Find Position Catchup Validate Query Data7/11/2012 16
    • Writes Accept Leader Prepare Accept Invalidate Apply7/11/2012 17
    • Observation - Availability7/11/2012 18
    • Observation – Latency7/11/2012 19
    • Conclusion  Megastore and its motivation  Features of megastore • It has ACID semantics • But need to define entity groups • Need to handle inter-group updates  Scalability and Availability  More experiments are needed7/11/2012 20