CMSC389L

Week 3

S3 + CloudFront

September, 15, 2017

Recap

Simple Storage Service (S3): Key-value store for object storage at scale
- Bucket + Key : Object
Object Storage: Any sequence of bytes (photos, videos, source code, ...)
Durability: 99.999999999%
- Replicated across data centers and AZs
Features: ACLs, Metadata, Versioning, Encryption, ...

S3 Use Cases: Think "file storage"
- Object Size: support for large files (up to 5TB)
- Integration with CloudFront CDN
- Support for archiving data (to Glacier)
- examples: website static content (HTML/CSS/etc.), log files
Non-S3 Use Cases: Databases -- think "queryable data"
- Object Size: Limited (f.e., 400Kb for DynamoDB)
- DBMS guarantees
  - Support for indexes for querying
- Faster read/writes
- examples: user profile data, credentials

Object: Fundamental entity in S3
- Consists of object data + metadata
- Metadata: name-value pairs that describe the object
  - date last modified, content-type, etc.
Bucket: Container for objects stored in S3
- Bucket name must be globally unique
- Can store unlimited objects
Key: Unique identifier of objects within buckets

Atomic: Reads to a previously updated object will return either the updated object or the previous object. Never partial or corrupted data.

Eventual Consistency: Update and delete operations are not available until fully replicated.
- For new keys, reads have read-after-write consistency

	S3 Default	S3 RRS	S3 IA	Glacier
Durability	99.999999999%	99.99%	99.999999999%	99.999999999%
Availability	99.99%	99.99%	99.9%	99.99%
Extra Fees *	None	None	Retrieval	None
Real-Time Access?	Yes	Yes	Yes	No (min to hours)
Frequently Accessed?	Yes	Yes	No	No

* : Excludes the usual data storage (per-GB), external bandwidth (GB/month), and API call charges

Content Delivery Networks (CDN): a globally-distributed network of proxy servers which cache content
- Use cases: web streaming, static content acceleration

Latency: Time taken until the first byte is downloaded
Data Transfer Rates: Rate at which data is transferred to the client
Cache Hit Ratio: The percent of requests where the data can be retrieved from the cache

Edge Locations: Proxy server in the CloudFront network
Regional Edge Caches: Proxy servers that intermediates between origin server and edge locations.

Origin Server: The definitive store of content that CloudFront will accelerate (f.e., S3 or EC2 web server)
Distribution: Configuration specifying your origin server, cache invalidation rules, etc.
- Shared with edge locations

Transfer from CloudFront to Internet: $0.085 / GB
- Varies by region and throughput
  - Drops to $0.020 / GB
Transfer from AWS (S3, etc.) to CloudFront: Free
Per-request fee: $0.01 / 10k requests

Complete the worksheet on CloudFront.