Page 141 -

The Greening of IT
106 How Companies Can Make a Difference for the Environment

Infrastructure Options and Plans

Although one of the primary benefits of server virtualization is consolida-
tion of resources, the implementation of virtual servers often leads to signifi-
cant increases in storage capacity. More than half (54 percent) of the
virtual-server adopters have experienced a net growth in capacity, whereas
only 7 percent reported a net decrease. ESG analysts believe those organiza-
tions reporting no change in capacity, or a decrease in capacity, might have
benefited from storage consolidation or other infrastructure initiatives as part
of their virtualization deployment and might simply be in the early stages of
implementation and have not yet reached the tipping point where they expe-
rience a net increase in storage capacity. However, the overall conclusion is
that server virtualization typically increases capacity requirements.
Together with performance and management demands, the increased stor-
age capacity requirements have a profound effect on how users design their
underlying storage infrastructures (for example, DAS, NAS, Fibre Channel
SAN, or iSCSI SAN). And in this context, it’s important to note that the vast
majority (72 percent) of users are sharing storage resources between virtual-
ized and nonvirtualized (physical) servers. Overall, there is a clear trend ptg
toward networked storage architectures (Fibre Channel SAN, iSCSI SAN,
and NAS), as opposed to DAS. For example, 86 percent of the ESG survey
respondents use networked storage, whereas only 14 percent are still relying
exclusively on DAS.
As might be expected, Fibre Channel SANs are preferred by larger organi-
zations, whereas DAS is often the preferred architecture for SMBs.
Surprisingly, however, adoption rates for iSCSI in virtual server environments
are about the same across all sizes of organizations (as is the case for NAS). In
any case, the trend toward networked storage in virtual server environments
is clear: Today, approximately 60 percent of users’ virtual server capacity is
networked, and that percentage is expected to increase to 74 percent over the
next 24 months. The most commonly cited benefits include better mobility
of virtual machines across physical servers (66 percent of survey respondents),
easier and more cost-effective disaster recovery, increased uptime and avail-
ability, more-efficient upgrades of physical servers, and high-availability
storage of multiple copies of virtual machine images (54 percent).

Storage Management Issues

Virtual servers force users to address storage management and data-
protection issues such as backup, remote replication, capacity planning, and