DistOS 2014W Lecture 19

Dynamo

• Key value-store.
• Build a distributed storage system:
• Scale
• Simple: key-value
• Highly available
• Guarantee Service Level Agreements (SLA).
• high concurrent.
• no dynamic routing.
• 0-hop DHT: means it is doe not have information when deliver packet from node to another , it has direct link to the destination
• Dynamo sacrifices consistency under certain failure scenarios.
• it has partition algorithm.
• Consistent hashing: the output range of a hash function is treated as a fixed circular space or “ring”.
• Key is linear and the nodes is partition.
• ”Virtual Nodes”: Each node can be responsible for more than one virtual node.
• Each data item is replicated at N hosts.
• “preference list”: The list of nodes that is responsible for storing a particular key.
• Sacrifice strong consistency for availability
• it work with 100 servers,it is not more big.

Bigtable

• BigTable is a distributed storage system for managing structured data.
• Designed to scale to a very large size
• it stores the column together ,the raw is web pages and the column is the contents.
• Each pages have incoming links
• A BigTable is a sparse, distributed persistent multi-dimensional sorted map.
• it have a many columns and it is look as table.
• Each raw has arbitrary column.
• It is multi daimination map.
• An SSTable provides a persistent,ordered immutable map from keys to values, where both keys and values are arbitrary byte strings.
• Large tables broken into tablets at row boundaries and each raw Tablet holds contiguous range of rows.
• Metadata operations: Create/delete tables, column families, change metadata