Flash SSD vs Magnetic Hard Disks

Flash combines speed of DRAM w/ persistance of disks

• access latency 100x faster
• transfer throughput 10-100x higher
• Read-write impact asymmetry; much lower lifetimes

NVRAM vs Magnetic Hard Disks

nvram - non volitile rame, similar capacity as SSD

Random R/W with less to no SSD-style wear and tear

• Byte-addressability (not blocks like SSDs/HDDs)
• Spatial locality of reference like DRAM; radical change!
• Latency, throughput, parallelism, etc. similar to DRAM
• Alas, yet to see light of day in production settings
• Cost per GB: No one knows for sure yet!

Review

How is a database different from a file?

• File systems store a collection of raw folders onto a hard disk, such as the directories on windows where as databases are a software system

What are the 2 levels of a database? Why the dichotomy?

• Physical: describes how data is stored, deals w/ actual implementation details of storage such as the data structures, file organization, access methods
• Logical: how data appears to users and applications, providing a conceptual view through tables, relationships, etc
• Motivation: provides abstraction and separation of concerns providing flexibility

What type of data modality is JSON meant to capture?

• semi structured data to represent data in a human readable format

Explain 2 differences between a relation and a DataFrame.