The document discusses the datacenter as a computer or warehouse-scale computer (WSC). Key points: 1. WSCs run large Internet services/applications across thousands of servers rather than single machines. 2. They must be designed to gracefully handle frequent component failures due to their large scale. 3. Building and operating such large computing platforms is very expensive, so cost efficiency across hardware, software, energy usage, and other factors is important to consider.

1. The Datacenter as a Computer
Introduction
2009/12/06
id:daisukebe

2. PC to Internet
• computing and storage are moving from
clients to Internet service
• email, photo, video, and office application...
• allow user to run at a low cost

3. Toward WSC
• the massive scale of their software
infrastructure, data repositories, and
hardware platform
• a departure from a single machine
• the program is an Internet service

4. Overview of WSC
• run a smaller number of very large
applications(or Internet services)
• must be designed to gracefully tolerate
large numbers of component faults
• building and operating a large computing
platform is expensive

5. Cost Efficiency
• building and operating a large computing
platform is expensive
• cost efficiency must be defined broadly to
account for all the components of cost

6. eg.
• Web search system is driven by the following:
1. Increasing popularity means higher request
loads
2. 1,000,000p/day means building a index
3. most substantial improvements demand
additional computing resources

7. What’s WSC?
• the machine, the computer, is the large
cluster or aggregation of servers itself and a
single computing unit
• WSCs have an additional layer of
complexity beyond systems consisting of
individual servers or small groups of server
• introduce new challenge to programmer
productivity, a challenge perhaps greater
than programming multicore systems

8. Why WSC?
• a rack with 40 servers, each with four 8-
core dual-threaded CPUs, would contain
more than two thousand H/W threads
• many org. will soon be able to afford
similarly sized computers at a much lower
cost
• this experience will be useful for ubiquitous
next-generation machines

9. Architecture
Typical elements in warehouse-scale systems: 1U server(left), 7`
rack with Ethernet switch(middle), and diagram of a small cluster
with a cluster-level Ethernet switch/router(right)

10. Architecture -Storage
• connecting directly to each individual
server(managed by GFS) or being part of
NAS?
• NAS provides extra reliability
• GFS implement replication across different
machines
• WSCs deploy desktop-class disk drives
instead of enterprise-grade disks

11. Architecture -Networking Fabric
• trading-off between speed, scale, and cost
• a switch that has 10 times the bi-section
bandwidth costs about 100 times as much
• intra rack connectivity is often cheaper
than inter rack connectivity

12. Architecture ~Storage Hierarchy
• DRAM and disk
resources within the
rack are accessible
through the first-level
rack switches
• all resources in the racks
are accessible via the
cluster-level switch

13. Latency, Bandwidth, Capacity
• the graph shows the latency, bandwidth, and
capacity of each resource pool

14. Latency, Bandwidth, Capacity
• these discrepancies are much larger than those
seen on a single machine
• a key challenge for architects of WSCs is to
smooth out these discrepancies in a cost-efficient
manner
• a key challenge for software architects is to build
cluster infrastructure and services that hide most
of this complexity from application developers

15. Power Usage
• energy-related costs
have become an
important component
of the total cost of
ownership
• CPUs can no longer
be the sole focus of
energy efficiency

16. Handling Failures
• the sheer scale of WSCs requires that
Internet services software tolerate
relatively high component fault rates
• an application running across thousands of
machines may need to react to failure
conditions on an hourly basis