Scalability and high availability

in the world of shared hosting

Igor Seletskiy,

CEO, CloudLinux

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Cloud vs Cluster

SAN vs NAS

Single server CP vs multi-server CP

VPS vs Shared Hosting

Scaling a site beyond single server

Cloud & Shared Hosting

Easy migrations

SAN ability to move to new hardware instantly

Grow your servers as needed

Out of the box CP (cPanel, Plesk)

Cloud Pitfalls

SAN

IO performance

Single point of failure

FSCK is still here

Hypervisor issues

Hypervisor System Failure Risks

Shared Hosting and Clustering

Load Balancer

NFS Shared Storage DBMail

Clustering - Benefits

Fault tolerance

No single point of failure

Scalability

Simplified backups

Clustering - Pitfalls

Complexity

Software failures

Configuration issues

Human Errors

Monitoring

Shared storage

No good control panel

Expensive

Shared Storage NFS is slow

Local Storage

Open

Read

.

Read

Close

Shared Storage

Local NFS server

Open

Read Open

Read

Close

Read Open

Read

Close

Close

Shared Storage

No alternatives to NFS

GlusterFS, Lustre, etc

Sessions

Where to store?

Memcache

Disk

Session affinity

Single server CP vs cluster CP

Cluster CP are difficult to do & maintain

Home made CPs tend to get outdated

GoDaddy switched to cPanel

cPanel & Plesk have more features than any

clustered/home made CP

No 3rd party extensions

Scalability Why VPS?

Site using too much resources

Site needs specific software

VPS cannot solve scaling beyond single server

CloudLinux HA platform

Cluster

No NFS (no shared storage)

Fully compatible with cPanel

On Demand high availability

Site scalability beyond single server

General Arch

LB cPanel Servers Web Appliances C&C server

INTERNET

C&C

Web Appliances Web Appliances Web Appliances cPanel cPanel

NGINX NGINX

cPanel

Acc 1

Acc 2

Acc 3

Acc 4

WA WA

cPanel Server

1:1 NAT

Enable account for high availability

Web Appliance

Hold sites from multiple cPanel servers

Automatically replicate sites if needed

NGINX

C&C

WA WA

C2A1 C1A1

C1A2 C1A2

Web Appliance

weakly shared file system: Inotify & lsyncd

CageFS

PHP Selector / Python / Ruby

Sessions

MySQL (socat/smart library)

Crontab -> cPanel

Sendmail -> cPanel

Other external commands -> cPanel

Future Shared File System

Mostly reads

Writes are rare

Locks are rare, can be costly

Locks can be costly

Resolve conflicts in favor of any

Other Components

MySQL

Mail

Future

What we call today Shared hosting can grow into a platform used to serve some of the most popular internet

resources

There should be no reason for a website

owner to move to VPS

If you want to learn more, talk to as at booth D20

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