Voldemort

Voldemort is a distributed key-value storage system.

Voldemort Logical Architecture

Functions

Data is automatically replicated over multiple servers.
Data is automatically partitioned so each server contains only a subset of the total data
Server failure is handled transparently
Pluggable serialization is supported to allow rich keys and values including lists and tuples with named fields, as well as to integrate with common serialization frameworks like Protocol Buffers, Thrift, and Java Serialization
Data items are versioned to maximize data integrity in failure scenarios without compromising availability of the system
Each node is independent of other nodes with no central point of failure or coordination
Good single node performance: you can expect 10-20k operations per second depending on the machines, the network, the disk system, and the data replication factor
Support for pluggable data placement strategies to support things like distribution across data centers that are geographical far apart.

Voldemort Physical Architecture

It is used at LinkedIn for certain high-scalability storage problems where simple functional partitioning is not sufficient.