istrators, there aren’t always clear connections among the
storage volumes, the workloads that each volume supports, the
demands against each volume, and who is consuming capacity.
“Essentially, the virtual infrastructure has created another
layer of abstraction on top of the storage infrastructure without
really freeing you from the complexity of the physical layer,”
Boles explains. “Now you have this virtual storage layer that
you’re managing, made up of [VMware’s] VMFS, all the different virtual server files and data, and you’re provisioning those
resources inside the virtual infrastructure — maybe even executing operations like Snapshot.” On top of all that, “you still
have to take care of the physical infrastructure and look at I/O
demand. Having those two layers makes it harder to connect
the dots between them,” he says.
HOW TO DEAL: Consider thin provisioning, a storage
virtualization capability that helps curb low storage utilization
by allocating data to free space. Physical storage is allocated on
demand from a shared pool, but only when needed.
By using thin provisioning along with server virtualization,
users can optimize both server and storage utilization rates.
Virtualization appliances and arrays from vendors such as
3Par, Compellent, DataCore Software and NetApp include thin
provisioning functionality.
4 The Need to Adapt the Storage Infrastructure to Serve Both Physical and Virtual Environments In a finding that’s similar to the backup and re- covery dilemma, 20% of the polled administrators said that they find it hard to adapt their storage infrastructure to handle a mix of traditional and virtual processes.
HOW TO DEAL: When jumping into virtualization solutions
that will mingle with physical environments, “make sure you’re
doing it with the best storage vendor you can find for ease of use,
simplicity and virtual infrastructure integration,” Boles says.
Some of the big vendors’ offerings are integrated with
the virtual infrastructure, reducing the complexity of these
systems “so you don’t have to do a lot crazy stuff, like disk group
configuration,” he adds. “You want one-click setup of storage
and [access to] fine-grain granularity provision storage so you
can carve up resources, understanding who’s using what, and
manage it over time.”
Some large-scale IT departments are even making a com-
plete switch to technologies like an NFS-NAS setup, which is
ready to go into production underneath a virtual infrastructure.
“You can store a whole bunch of virtual machines on one
storage mount point and not have a lot of complexity around
that,” says Boles. “There aren’t nearly as many headaches as
trying to coordinate some of those physical storage resources
with a very virtual server infrastructure.”
5 Trouble Choosing the Right Kind of Networked Storage for Virtualized Servers Some 18% of the storage professionals surveyed said that they can’t decide on the right kind of
networked storage for virtualized servers.
“The right kind of networked storage makes a difference —
because you can scale, and get better performance and more
simplicity in your processes [if you choose correctly],” Boles
says. But the right solution depends largely on the organization’s objectives.
At Purdue University’s Krannert School of Management, for instance, the I T department’s top priority wasn’t 24/7 availability for
its virtualized environment, but rather fast recovery time when
— not if — the system went down, says I T manager Jeff Ellow.
Virtualizing storage-intensive servers without big performance losses requires a level of storage performance that SANs
weren’t able to achieve. The obvious choice for Purdue seemed
to be 10 Gigabit iSCSI, but cost was a deterrent.
Purdue ultimately went with LSI 6Gbps SAS switching
technologies, which offered the benefits of a failover SAN and
the performance of an end-to-end native SAS 6Gbps data path
—and which the school could afford.
“Even if our SAN goes down, we have enough local storage
where we could limp along in another mode. Restoring more
quickly is more important than staying up,” Ellow says.
HOW TO DEAL: Before choosing any vendor, be sure you
understand the management capabilities, Barnes says. Server
and storage virtualization can be simple: “You don’t have to be
a rocket scientist or have a degree in SAN management to take
care of these things,” he says.
At the end of the day, Elam says the benefits of virtualization
are worth the trouble of grappling with these five challenges.
“The pros far outweigh the cons just in its complete ease
of use, stability, high availability, being able to replicate and
do maintenance during the day, move stuff around as you need
to and take hardware offline,” he says “There are lots of things
you don’t have to come in on a weekend to do anymore.” u
Collett is a Computerworld contributing writer. You can contact
her at stcollett@aol.com.
Even if our SAN goes down, we have enough local storage
where we could limp along in another mode. Restoring more quickly
is more important than staying up.
