ESG WHITE PAPER

Making IT Invisible

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Copyright     2008, The Enterprise Strategy Group, Inc. All Rights Reserved.  

and reduced backup windows. When implementing server virtualization solutions, there are a number of

important issues to consider, including:

 

1.   Capacity Planning: In the physical world, the operating system and applications are traditionally

stored on local disks within the physical server. However, in virtualized environments, the virtual

machine images, including the guest operating system, applications and associated data, are all

stored on networked storage. Server consolidation efforts will require careful capacity planning as

companies make it a strategic, company-wide initiative and more servers are virtualized. Another

primary driver for implementing server virtualization is its inherent ability to provide business

continuance and disaster recovery solutions. This means that multiple copies (and snapshots) of

virtual machines are created and stored in both the primary and secondary data centers. The storage

capacity impact of virtual servers is significant and will largely depend on the servers and applications

targeted for a virtualized infrastructure.

2.   Storage Tiers: Not all virtual machines and applications require the same level of performance and

availability. This is especially true as the virtual machine and its associated data move from

test/development to a production environment. ESG typically sees organizations configuring two to

three different tiers of storage based on performance and protection requirements, as well as price.

3.   Zoning: The physical servers that are running the virtualization software and utilizing networked

storage for load balancing and failover must all be in the same zone. In large scale deployments,

creating one zone may not be practical or possible, so it will make sense to logically create multiple

zones based on application and workload functionality.

4.   LUN Creation: When creating LUNs on the storage system, you will need to determine if you want

many small LUNs or fewer, larger LUNs. Creating fewer large LUNs will be easier to manage and

give the virtual server administrator greater flexibility, while creating multiple smaller LUNs can help

avoid I/O contention and provide granular RAID characteristics that closely match application

requirements. There is not a simple answer as to the best approach to take, and it may require

running the applications to see if disk performance is acceptable and tweaking the size of the LUN

and RAID level accordingly to achieve optimal performance.

5.   Networked Storage Administration: Traditional storage resource management (SRM) tools will only

have visibility to the Fibre Channel HBA on the host operating system (e.g., VMware ESX Server) and

cannot directly access the virtual machine operating system that utilizes the storage. The virtual

machines will play hide and seek from SAN administration tools, which will force reliance on the

server   virtualization   management   tools   to   supervise   the   individual   virtual   machines.   N-Port

Virtualization (NPIV), a technology that virtualizes world wide names (WWNs) and assigns a unique

WWN to each virtual machine, will allow storage management tools to work again, but NPIV is not yet

supported across all server virtualization solutions and not all HBAs are compatible with NPIV. It is

also worth noting that iSCSI and NAS implementations will not have this limitation since each virtual

machine has a unique IP address.

 

Customers understand why networked storage is required for effective server virtualization environments.

When it comes to server virtualization environments, networked storage options of all types offer significantly

better flexibility, availability, performance and mobility when compared to DAS solutions.