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Best practices for NAS arrays: Avoid file management nightmares by planning
About 15 years ago, in the days
when NetApp was known as Network Appliance, the company set out to make a
network-attached storage (NAS) system that would be easy to use and easy to
Today's NAS products remain true to that
"The reality of the situation is that just
about every NAS box you can buy today, from startups or from established
players, is up and running in 20 minutes," says Arun Taneja, founder and
president of the Taneja Group, a consulting firm that focuses on storage
technologies. "They're all very easy to use."
Storage administrators who want to tailor their
NAS arrays to work with certain applications or under specific situations can
easily find countless white papers and guides on NAS vendor websites.
And sometimes it does pay to read the fine
print, as the Sacramento Superior Court learned the hard way in July. No one in
the IT department there had noticed NetApp's recommendation to use a dedicated
connection for each of the ports in its Cisco switch until it was too late.
Since the switch is responsible for 90% of the court's servers, there was
substantial downtime while the IT staff diagnosed the problem. Now that the
Ethernet module has been upgraded, performance has spiked dramatically,
according to Lewis Walker, a senior IT analyst at the state court.
But beyond consulting the white papers, there
are five universal best practices that apply to NAS arrays.
Best Practice #1. Plan ahead, make future needs your top priority
Walker advises his storage peers to take into
account their anticipated product replacement cycles as they assess their
long-term storage needs. If it's four years, they need to size out the
environment as best they can with that endpoint as the goal. But he also
recommends they build in some headroom for unanticipated requests.
"Once you get the technology, someone's going
to want to adapt it to do something that no one thought of," Walker says.
"Everybody wants to use it.
The Sacramento Superior Court reached the limit
of 12 disk shelves on its NetApp FAS 3020 within three years and recently put in
a purchase order to upgrade to the FAS 3140, which can take 30 disk shelves,
According to Taneja, users tend to like their
first NAS boxes so much that they can fill them up within a few months, if
they're not careful. Then they go get a second box and changes need to be made
on the client side so the computer knows where to find the files, which, he
notes, is "not trivial if you've got 2,000 users." When the second box reaches
capacity, the company adds a third and a fourth and so on, until they find
themselves with a management nightmare.
"NAS has a habit of growing like rabbits, and
the more rabbits you have, the bigger your headache," Taneja says. He advises
clients to do a systematic analysis before installing NAS, but "usually they
come to me when they've bashed their heads, and they're already at a hundred."
When weighing expansion plans, administrators
also need to think about what sorts of policies they might put in place, such as
limits on MP3 files or personal data. They should use management tools to study
how the NAS array is being used, how many files are in the system and how many
are active to gain insight into how they can manage more effectively.
"The administrators of the NAS system, at some
point, have to ask themselves whether they can just keep buying storage," says
Robert Passmore, an analyst at Gartner Inc., noting that "some people establish
quotas, which forces the users occasionally to go back and delete files." But
the quota system, he says, is "disruptive to the organization." Automatic
archiving of files that are no longer in use onto lower cost media is a better
Best Practice # 2. Tier the data and automate the process
All disks are not created
equal. A Fibre Channel drive might spin at 15,000 rpm, but it's also far too
costly and power-hogging to use for low-priority data. Less important files
might make more sense on a cheaper, power-efficient, high-density SATA drive
spinning at 5,400 rpm.
But putting the data on the right type of disk at the right time – or
tiering – isn't enough, according to Brad Bunce, EMC's director of product
marketing for NAS platforms. "Tiering the data allows you to control your
costs from a disk perspective," he says. "The key is to have automation in
the tiering. The last thing administrators want to be doing is running
reports to find stale data and then manually move it."
Bunce described how the
process works in an EMC storage system that permits different drive types in
the same array. A Celerra file-mover API leveraged with EMC's Rainfinity
file management appliance (FMA) allows users to automate the movement of
data based on policies
If a policy calls for relocating files that
haven't been accessed for 30 days, the FMA moves the file from the
high-performance disk to the low-performance disk. A stub is left behind to the
real file location, so a user or application doesn't know the file has moved.
When the file is recalled, the client can directly access the file at its new
Another option is selecting products from
different storage vendors. The Sacramento Superior Court uses NetApp's FAS
midrange systems for its most mission-critical data but opted for a lower-cost
Hewlett-Packard NAS box running Microsoft's Windows Storage Server for less
important, second-tier data, such as employees' private drives. The court
sacrifices useful features, such as thin provisioning and data deduplication
with the HP system, which it must manage separately, but the cost savings have
been substantial, says Walker.
"As good as NetApp is, they are expensive," he
says. "You get what you pay for."
Best Practice #3. Thin provision whenever possible
With thin provisioning, an administrator sets
the high-water mark for the storage's ultimate limit, then provisions only a
small amount to start, allowing the NAS array to automatically grow the file
systems or iSCSI LUNs as users request more storage. Alerts warn administrators
when they're due to run out of physical storage so they can add capacity on the
fly, nondisruptively, to keep operations humming.
The leaders in the NAS space, NetApp and EMC,
offer thin provisioning to maximize storage efficiency, as do many other
vendors. "Set it and forget it," is how EMC's Bunce describes the process. A
simple checkmark in the company's Celerra storage system enables the feature,
which prevents administrators from over-provisioning and allows them to leverage
unused capacity for other purposes, if necessary.
Best Practice #4. Take snapshots of the data
Creating logical point-in-time copies of the
data will pay off the first time a file is lost, corrupted or accidentally
deleted. Restoring data from the snapshot is quick compared to the
time-consuming ordeal of going to the tape or some other subsystem. Plus,
snapshots consume little space, have no impact on performance and even permit
users to recover the data on their own, if enabled.
"Make sure that snapshot gets backed up
somewhere," warns Greg Schulz, founder of StorageIO Group. The backup can be on
another NAS array, a disk or a tape, he says. "The array might be set up to do
snapshots on its own, but if something happens to that array, your backup just
went away. In other words, be in total protection."
Best Practice 5. Secure the array and the data
With NAS, a storage administrator is attaching
to a network, and that's the value proposition of NAS: to be able to share over
a network. "That's the good news," Schulz said. "The bad news is you are going
to share over a network, which means you have the potential that unauthorized
people could access that data."
So the file systems need to be secured.
Authentication mechanisms need to be put in place. Authorizations need to be set
so only the appropriate users are permitted to access certain files.
Administrative privileges need to be established to limit the number of people
who can change the settings. Management tools and interfaces also need to be
"There's both administrative and user security
around files," Passmore said.
The Sacramento Superior Court uses Microsoft's
Active Directory in conjunction with its NAS array to avoid the "administrative
nightmare" of having to update user rights in two places, Walker says.
Also important is implementing best practices
for virus protection, since a file stored on a NAS system could be infected.
Vendors typically provide instructions for doing this.