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EC2: Avanzado

Henry Alvarado

Arquitecto de soluciones

Amazon Web Services

• What is the EC2 instance platform and a

virtualization primer

• How to make the most of your EC2 instance

experience through the lens of three instance types

• How to think about the future of EC2 instances

Agenda

EC2 Instance Platform

EC2EC2

Amazon EC2 Instances

Host Server

Hypervisor

Guest 1 Guest 2 Guest n

c3.largeInstance family

Instance generation

Instance size

Virtualization Primer: x86 CPU

• Prior to Intel VT-x – Binary translation

– Para-virtualization (PV)

• After Intel VT-x– Hardware assisted virtualization (HVM)

• PV vs. HVM Amazon Machine Images

• vCPU scheduling choices and variability

Host Server

Hypervisor

Guest 1 Guest 2 Guest n

Virtualization Primer: I/O and Devices

• Scheduling I/O requests between virtual devices

and shared physical hardware

• Split driver model for shared devices; requires

host resources

• Intel VT-d– Direct pass through and IOMMU for dedicated devices

Our Philosophy

• Bigger, faster, less expensive, consistent,

and flexible

• Our bar is bare metal performance

• Customers help us prioritize our

roadmap

• Look under the hood through the lens

of three recent platforms: C4, T2, and I2

Make the most of your experience

T2 Instances: Low Cost

Review: T2 Instances

• Lowest cost EC2 instance at $0.013 per hour

• Burstable vs. Fixed Performance

Name vCPUsBaseline

PerformancePlatform RAM (GiB)

CPU Credits /

Hour

t2.micro 1 10% 32-bit or 64-bit 1 6

t2.small 1 20% 32-bit or 64-bit 2 12

t2.medium 2 40% 32-bit or 64-bit 4 24

t2.large 2 60% 64-bit 8 36

Tip: Understand CPU credits

• http://aws.amazon.com/blogs/aws/low-cost-

burstable-ec2-instances/

• http://aws.amazon.com/ec2/instance-types/t2/

• Attend this session

How Credits Work

Baseline Rate

Credit

Balance

• A CPU Credit provides the

performance of a full CPU core for

one minute

• An instance earns CPU credits at

a steady rate

• An instance consumes credits

when active

• Credits expire (leak) over time

Burst

Rate

CPU Credits

• A CPU Credit provides the performance of a full

CPU core for one minute

• Hefty initial CPU credit balance for good startup

experience

• Use credits when active, accrue credits when

idle

• Transparency on credit balances

Tip: Monitor CPU credit balance

I2 Instances: High I/O

Review: I2 Instances

• 16 vCPU: 3.2 TB SSD; 32 vCPU: 6.4 TB SSD

• 365K random read IOPS for 32 vCPU instance

Model vCPU Memory

(GiB)

Storage Read IOPS Write IOPS

i2.xlarge 4 30.5 1 x 800 SSD 35,000 35,000

i2.2xlarge 8 61 2 x 800 SSD 75,000 75,000

i2.4xlarge 16 122 4 x 800 SSD 175,000 155,000

i2.8xlarge 32 244 8 x 800 SSD 365,000 315,000

Tip: Use 3.8+ kernel

• Amazon Linux 13.09 or later

• Ubuntu 14.04 or later

• RHEL7 or later

• Etc.

Pre-3.8.0 Kernels

• All I/O must pass through I/O Domain

• Requires “grant mapping” prior to 3.8.0

• Grant mappings are expensive operations due to TLB flushes

read(fd, buffer, BLOCK_SIZE)

3.8.0+ Kernels – Persistent and Indirect

• Grant mappings are setup in a pool once

• Data is copied in and out of the grant pool

• Copying is significantly faster than remapping

read(fd, buffer, BLOCK_SIZE)

Tip: Issue TRIM or Overprovision

SSDs and Wear Leveling

• FLASH has a limited number of writes per physical sector– Sectors wear out; must be erased before being rewritten to

– Erasing actually sets values to all 1s, slow

• Modern drive firmware is very sophisticated to extend life of FLASH

• TRIM and/or over provisioning helps avoid garbage collection and write amplification

Flash Translation Layer

• All new writes go to TAIL

• Random write == Sequential write

• Even sector wear (Wear Leveling)

HEAD

TAIL

Garbage Collection

• New writes have to search for free space

• Results in garbage collection pauses

• Large writes may require defragmentation

HEAD

TAIL

C3 Instances: High Compute

Review: C3 Instances

• Intel E5-2680 v2 at 2.8 GHz

• Enhanced networking

Model vCPU Memory (GiB) Storage (GB)

c3.large 2 3.75 2 x 16 SSD

c3.xlarge 4 7.5 2 x 40 SSD

c3.2xlarge 8 15 2 x 80 SSD

c3.4xlarge 16 30 2 x 160 SSD

c3.8xlarge 32 60 2 x 320 SSD

Tip: Use PV-HVM AMIs with EBS

Why PV-HVM is faster than PV

• PV-HVM allows Application to call directly into the Kernel

• PV requires going through the VMM

• Applications that are system call bound are most affected

Kernel

Application

Kernel

Application

VMM

Application

VMM

Kernel

Bare Metal PV-HVM PV

Tip: Use TSC as clocksource

Time Keeping Explained

• Time keeping in an instance is deceptively hard

• gettimeofday(), clock_gettime(), QueryPerformanceCounter()

• The TSC

– CPU counter, accessible from userspace

– Requires calibration, vDSO

– Invariant on Sandy Bridge+ processors

• Xen pvclock; does not support vDSO

• On current generation instances, use TSC as clocksource

Summary

Summary

• Just scratching the surface

• Visit the EC2 Instance Documentation for more tips and

tricks

EC2EC2