1. CS 140 Lecture Notes: Technology and Operating Systems Slide 1 Technology Changes Mid-1980’s2012Change CPU speed15 MHz2.5 GHz167x Memory size8 MB4 GB500x Disk capacity30 MB500 GB16667x Disk transfer rate2 MB/s100 MB/s50x Network speed10 Mb/s1 Gb/s100x

2. ● Can’t afford to page out unless idle for a long time CS 140 Lecture Notes: Technology and Operating Systems Slide 2 Role of Paging 1960’sTodayChange Disk latency80 ms10 ms8x Disk transfer rate250 KB/s100 MB/s400x Memory size256 KB4 GB16000x Time to replace all of memory (random) 6.4 s3 hours1500x Time to replace all of memory (sequential) 1 s40 s40x

3. DRAM in Storage Systems Usage exploding, but: ● Clumsy (consistency with backing store) ● Lost performance (cache misses, backing store) CS 140 Lecture Notes: Technology and Operating Systems Slide 3 19701980199020002010 UNIX buffer cache Main-memory databases Large file caches Web indexes entirely in DRAM memcached Facebook: 200 TB total data 150 TB cache! Main-memory DBs, again

4. General-purpose storage in DRAM: ● All data always in DRAM (no cache misses) ● As durable and available as disk ● Designed for datacenters:  Scale: 1000+ servers, 100+ TB  Low latency: 5-10µs remote access Potential impact: enable new class of applications CS 140 Lecture Notes: Technology and Operating Systems Slide 4 RAMCloud

5. CS 140 Lecture Notes: Technology and Operating Systems Slide 5 RAMCloud Architecture Master Backup Master Backup Master Backup Master Backup … Appl. Library Appl. Library Appl. Library Appl. Library … Datacenter Network Coordinator 1000 – 10,000 Storage Servers 1000 – 100,000 Application Servers Commodity Servers 64-256 GB per server High-speed networking: ● 5 µs round-trip ● Full bisection bwidth

6. create(tableId, blob) => objectId, version read(tableId, objectId) => blob, version write(tableId, objectId, blob) => version cwrite(tableId, objectId, blob, version) => version delete(tableId, objectId) CS 140 Lecture Notes: Technology and Operating Systems Slide 6 Data Model: Key-Value Store Tables Identifier (64b) Version (64b) Blob (≤1MB) Object (Only overwrite if version matches) Richer model in the future: Indexes? Transactions? Graphs? Richer model in the future: Indexes? Transactions? Graphs?

7. CS 140 Lecture Notes: Technology and Operating Systems Slide 7 Research Issues ● Durability and availability ● Fast communication (RPC) ● Data model ● Concurrency, consistency, transactions ● Data distribution, scaling ● Multi-tenancy ● Client-server functional distribution ● Node architecture

8. CS 140 Lecture Notes: Technology and Operating Systems Slide 8