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RAMCloud: a Low-Latency Datacenter Storage System

RAMCloud: a Low-Latency Datacenter Storage System. John Ousterhout Stanford University ouster@cs.stanford.edu. Introduction. RAMCloud: new class of datacenter storage All data always in DRAM Large scale: 100 - 10,000 storage servers 100 TB - 1 PB total capacity Low latency:

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RAMCloud: a Low-Latency Datacenter Storage System

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  1. RAMCloud: a Low-Latency Datacenter Storage System John Ousterhout Stanford University ouster@cs.stanford.edu

  2. Introduction • RAMCloud: new class of datacenter storageAll data always in DRAM • Large scale: • 100 - 10,000 storage servers • 100 TB - 1 PB total capacity • Low latency: • 5 µs remote access time from anywhere in datacenter • Durable/available • Overall goal: enable a new class of applications Does this make sense for Radio Astronomy apps? Exascale Radio Astronomy Conference

  3. Traditional Storage Choices Exascale Radio Astronomy Conference

  4. RAMCloud Architecture 1000 – 100,000 Application Servers High-speed networking: • 5 µs round-trip • Full bisection bwidth … Appl. Appl. Appl. Appl. Library Library Library Library DatacenterNetwork Coordinator Master Master Master Master CommodityServers Backup Backup Backup Backup … 64-256 GBper server 1000 – 10,000 Storage Servers Exascale Radio Astronomy Conference

  5. Data Model: Key-Value Store Object Tables • Basic operations: • read(tableId, key) => blob, version • write(tableId, key, blob) => version • delete(tableId, key) • Other operations: • cwrite(tableId, key, blob, version) => version • Enumerate objects in table • Efficient multi-read, multi-write • Atomic increment • Under development: • Secondary indexes • Atomic updates of multiple objects Key (≤ 64KB) Version (64b) Blob (≤ 1MB) (Only overwrite ifversion matches) Exascale Radio Astronomy Conference

  6. Data Durability • One copy of data in DRAM • Multiple copies on disk/flash • Each master’s backup data scattered across cluster • Fast crash recovery • Remaining servers work together to recover lost data • Typical recovery time: 1-2 seconds Exascale Radio Astronomy Conference

  7. RAMCloud Performance • Using Infiniband networking (24 Gb/s, kernel bypass) • Other networking also supported, but slower • Reads: • 100B objects: 5µs • 10KB objects: 10µs • Single-server throughput (100B objects): 700 Kops/sec. • Small-object multi-reads: 1-2M objects/sec. • Durable writes: • 100B objects: 16µs • 10KB objects: 40µs • Small-object multi-writes: 400-500K objects/sec. 1 client, 1 server Exascale Radio Astronomy Conference

  8. Comparisons Exascale Radio Astronomy Conference

  9. RAMCloud Status • Ongoing research project at Stanford • Goal: production-quality system • Source code freely available • Version 1.0 tagged in January 2014(first version suitable for real applications) • Starting to work with early adopters • System requirements: • x86 servers (minimum cluster size: 10-20 servers) • Linux operating system • Need networking with kernel-bypass NICs • Built-in support for Mellanox Infiniband • Driver for SolarFlare 10 Gbs Ethernet NICs under development Exascale Radio Astronomy Conference

  10. Is RAMCloud Right for You? Issues to consider: • Remote access data model • Sparse vs. bulk • Key-value store • Durability Exascale Radio Astronomy Conference

  11. Large-Scale Applications D D D D D D D D D D C C C C C C C C C C • Remote data access • Works best for: • Sparse and unpredictable data accesses • No locality • Performance dominated by latency • Example: transactional Web applications (Facebook) • Computation, data colocated • Works best for: • Bulk processing (touch all data) • High locality of access • Performance dominated by bandwidth • Examples: analytics C C C C C C C C C C Network Computation Nodes StorageNodes Network D D D D D D D D D D Exascale Radio Astronomy Conference

  12. Conclusion • RAMCloud: general-purpose DRAM-based storage • Scale • Latency • Goals: • Harness full performance potential of DRAM-based storage • Enable new applications: intensive manipulation of large-scale data • What could you do with: • 1M cores • 1 petabyte data • 5-10µs access time Exascale Radio Astronomy Conference

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