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 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.