SQL Clusters in Virtualized Environments

April 10th, 2013

This session’s primary objective is to help you gain insight into where

clustering fits in the overall picture of HA/DR as it relates to MS SQL Server,

what it needs to work properly, as well as what considerations should go

into virtualizing MS SQL server clusters. This primarily concentrates around

technologies contained in the Microsoft’s latest version of their hypervisor,

Hyper-V R3.

I will be posting up instructions on how to set up a lab for testing SQL

virtualization and clustering using Hyper-V

Session Overview

� SQL High Availability options

� What are clusters?

� Clustering SQL Server

� Types of SQL clusters

� Resources needed

� Multi-Instance Cluster Considerations

� Virtualizing SQL Clusters

� Benefits

� Pitfalls

� Cluster Configuration

� Backup Considerations

� Sources Used

� Questions

� Contact Information

Session Review

SQL High Availability Options

Types of Clusters� Majority Node Cluster

� Each Node has it’s own local storage that it uses to store

and access the data

� Data is stored across multiple disks, synchronization

ensured by the cluster service

� Single Quorum Cluster

� Requires shared storage

� Used for storage-centric applications, such as SQL,

Exchange

What are clusters?A cluster is a group of independent systems working together as a one

to provide a highly available service or application. If a member of the

group fails, the others take over the load.

� Active-Passive Single Instance cluster

� Single instance, running on one node.

� In case of failure, fails over to another node

� Active-Active Multi-Instance Cluster

� Multiple Instances running on multiple nodes

� In case of failure, fails over to another node

� NOT A LOAD BALANCING

SOLUTION!!!

Clustering SQL ServersTypes of SQL Clusters

Clustering SQL ServersThree-node, three-instance cluster

Clustering SQL Server Resource Needed

� Networking

� 3 networks

� Data

� iSCSI

� Cluster traffic (heartbeat)

� Storage

� Create separate LUNs for SQL

� Use appropriate RAID levels for your

configuration

� If using virtual storage, conduct I/O tests to

ensure proper data transfer rates

Clustering SQL ServersResource provisioning – Multi-Instance Clusters

� Memory

Ensure that sufficient resources are in place

to tolerate failure of at least 1 node

� Each Server must have sufficient resources to run

all clustered instances

� Configure maximum memory usage at the

instance level to ensure performance after

failover

� Ports

Change the port on the second instance to

ensure both can coexist on the same server

Virtualizing SQL Clusters Benefits

� Business Continuity through vMotion/Live Migration

� Easier addition of resources

� Can eliminate storage as a single point of failure

� Eliminates expressed need for a SAN

� Designed for consolidation, not performance

� 10% performance hit

� Memory Overcommit/Dynamic Memory

� Virtual Disks

Virtualizing SQL Clusters Pitfalls

Virtualizing SQL Clusters I/O Performance Virtual Disk vs. Pass-Through Disk

Virtual Disk Pass-Through Disk

IO/S Latency (MS) IO/S Latency (ms)

Min Max Average Min Max Average

Random Reads 1545.04 124 6322 2623 11511.74 25 1167 354

Random Writes 1173.88 4 6616 3469 10149.12 31 1715 402

Sequential Reads 1631.54 120 5278 2496 10926.07 27 1114 373

Sequential Writes 1157.9 125 6766 3519 13376.58 18 1033 305

Virtualizing SQL Clusters Cluster Configuration

� Requires 3 virtual networks

� Data

� Storage

� Cluster Heartbeat

� Cluster VM’s preferred host servers should be set to separate hosts

� Avoid contention

� Avoid using thin provisioning/dynamic disks to avoid first write penalty

� Using memory overcommit/dynamic memory IS NOT RECOMMENDED

� If using memory overcommit/dynamic memory, set the minimum amount of

memory to the minimum needed for the SQL server, and increase the load

preference be the highest of all servers

� Test storage to ensure proper response

� SQLIO - http://www.microsoft.com/en-us/download/details.aspx?id=20163

� IOMETER - http://www.iometer.org/doc/downloads.html

Virtualizing SQL Clusters Backup Considerations

� VM Backup software issue

� Cannot read cluster volumes on the guests

� This means that backup software designed to backup the guests will not backup the SQL data

� Backup Exec Hyper-V agents

� VEEAM

� Use SQL to backup the database and logs to flat files

� Back up to a Network Share

� Ensure that normal SQL backup best practices are followed

� TEST YOUR BACKUPS!!!

� User your regular Hyper-V VSS aware backup software

� This will transfer your backup files to your favorite backup storage media

� TEST YOUR BACKUPS!!!

� Installing a SQL Server 2008 R2 Failover Cluster – TechNet– Microsoft’s official guide on installing a SQL server cluster

� http://www.mssqltips.com – excellent resource for day to day SQL server questions

� http://www.sqlha.com – If you are considering SQL high availability solution, check out this site first.

� http://blogs.msdn.com/b/momalek/archive/2012/04/18/creating-an-active-active-sql-cluster-using-hyper-v-part3-the-active-active-configuration.aspx - A walkthrough on configuring a multi-instance cluster in Hyper-V R3

Sources used/further reading

QUESTIONS ???

Contact Information

Thank you!

If you have more questions, I can be reached at:

Email – irubinshteyn@ceservices.com

Phone – 508-983-1962

Linked In - www.linkedin.com/pub/ilya-rubinshteyn/4/7b3/746/