Click to edit Master title style Literature Review Interconnection Architectures for Petabye-Scale High-Performance Storage Systems Andy D. Hospodor, Ethan L. Miller IEEE/NASA Goddard Conference on Mass Storage Systems and Technologies April 2004 Henry Chen September 24, 2010

Introduction  High-performance storage systems –Petabytes (2 50 bytes) of data storage –Supply hundreds or thousands of compute nodes –Aggregate system bandwidth >100GB/s  Performance should scale with capacity  Large individual storage systems –Require high-speed network interface –Concentration reduces fault tolerance

Proposal  Follow high-performance computing evolution –Multi-processor networks  Network of commodity devices  Use disk + 4  12port 1GbE switch as building block  Explore & simulate interconnect topologies

Commodity Hardware  Network –1Gb Ethernet: ~$20 per port –10Gb Ethernet: ~$5000 per port (25x per Gb per port) ● Aside: Now ~$1000 per port  Disk drive –ATA/(SATA) –FibreChannel/SCSI/(SAS)

Setup  Target 100GB/s bandwidth  Build system using 250GB drives (2004) –4096 drives to reach 1PB –Assume each drive has 25MB/s throughput  1Gb link supports 2  3 disks  10Gb link supports ~25 disks

Basic Interconnection  32 disks/switch  Replicate system 128x –4096 1Gb ports –128 10Gb ports  ~Networked RAID0  Data local to each server

Fat Tree  Gb ports  Gb ports –2048 switch to router (128 Sw × 8 Rt × 2) –112 inter-router –256 server to router (×2)  Need large, multi-stage routers  ~$10M for 10Gb ports

Butterfly Network  Need “concentrator” switch layer  Each network level carries entire traffic load  Only one path between any two server and storage

Mesh  Routers to servers at mesh edges  Gb links  Routers only at edges; mesh provides path redundancy

Torus  Mesh with edges wrapped around  Reduces average path length  No edges; dedicated connection breakout to servers

Hypercube  Special-case torus  Bandwidth scales better than mesh/torus  Connections per node increases with system  Can group devices into smaller units and connect with torus

Bandwidth  Not all topologies actually capable of 100GB/s  Maximum simultaneous bandwidth Link speed × number of links Average hops

Analysis  Embedding switches in storage fabric uses fewer high-speed ports, but more low-speed ports

Router Placement in Cube-Styles  Routers require nearly 100% bandwidth of links  Adjacent routers cause overload & underload  Use random placement; optimization possible?

Conclusions  Build multiprocessor-style network for storage  Commodity-based storage fabrics can be used to improve reliability and performance; scalable  Rely on large number of lower-speed links; limited number of high-speed links where necessary  Higher-dimension torii (4-D, 5-D) provides reasonable solution for 100GB/s from 1PB