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.