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Building on SANs: Getting the most from virtualized storage

Deploying a SAN is only the first step for reaping the benefits of virtualized storage. Tiered storage, thin provisioning and data replication are essential management strategies.

The life of an emergency room patient depends on fast data retrieval. Once the patient is out of the emergency room, however, data from that visit must be stored for decades.

To satisfy these conflicting requirements under ever-tightening budgets, hospitals and clinics are deploying virtualized storage in both Fibre Channel and iSCSI storage-area networks. A SAN creates logical data storage volumes distinct from the physical disk drives on which the data is stored. The abstracted data storage volumes can be organized, managed and moved to the most cost-effective physical medium, thus shortening response time, increasing reliability and lowering costs.

Deploying SANs is essential to achieve the benefits of today's storage technologies, and SANs are commonly used in virtualized storage environments -- but it's only a first step. To get the most out of virtual storage, health care providers must manage data storage efficiently. Three technologies -- tiered storage, thin provisioning and data replication -- have emerged as essential tools for managing data across virtualized storage environments:

  • Tiered storage assigns data to two or more tiers according to how frequently the data needs to be accessed. For example, hot data, such as an emergency department patient record, must be accessed frequently for a short time, so it's assigned to first-tier storage. After that, it will be accessed infrequently, but has to be stored for a long time, so it goes into second- or third-tier storage.
  • Thin provisioning utilizes a "pool" of virtual storage that can be allocated to applications and servers as it is needed. Thin provisioning saves money on disk drive hardware. It is particularly valuable in storing picture archiving and communication system (PACS) imaging files, which can be quite large.
  • Data replication is the process of copying data from one SAN to another so that it is available for disaster recovery and can be moved from one data center to another. Data may be replicated either asynchronously (to the primary storage array first) or synchronously (to the primary and secondary arrays simultaneously), and either locally or to a remote disaster recovery site.

Virtualized storage is a good match for health care providers because they are trying to save money on technology to provide better care, according to one analyst. "The more efficient IT you have, the more money that is available to treat patients," said Mark Peters, an analyst with the Milford, Mass.-based Enterprise Strategy Group Inc., a consultancy specializing in IT infrastructure.

Virtualized storage is not just about saving money, however. The practice can improve the quality of health care itself, Peters asserted. "Most of us are healthy most of the time. But when we're unhealthy, our data needs to be accessed quickly. Thin provisioning and tiered storage are valuable to almost any industry, but their value in health care is amplified because of this."

In addition to enabling rapid, repeated access to records when a patient is hospitalized, tiered storage can make it practical to save records for long periods by moving them to less expensive storage media. "When it comes to health care, you're talking about life spans," Peters said. "You might [even] want records for heredity studies and genetic analysis."

Tiered storage, thin provisioning can work hand in hand

Cambridge Health Alliance, a hospital network based in Cambridge, Mass., has established two tiers of storage to handle 90 terabytes (TB) of data. The first tier consists of two Fibre Channel SANs. The second tier is an iSCSI SAN with Fibre Channel ATA, or FATA, drives.

Virtualized storage is a good match for health care providers because they are trying to save money on technology to provide better care.


The network relies on 3PAR Adaptive Optimization virtualization management technology to manage data storage automatically across this multi-tiered architecture, as well as to handle thin provisioning. (Hewlett-Packard Co. acquired 3PAR in September 2010.)

"It helps us to dynamically tier our storage and use thin provisioning. It helps us cut our maintenance and administration costs," said Jim LaPlante, senior director of IT technical services at Cambridge Health.

One new wrinkle for the hospital network is the addition of "tier 0," a third tier of storage consisting of solid-state storage within the Fibre Channel SANs. "We're looking at that to solve some particular disk I/O pain points. There are some processes that require intensive I/O," said LaPlante, adding that he will deploy 3PAR's software version 2.4 to manage it.

"The tier of storage will be based on what activity at a given moment is requiring the greatest I/O demand. It could be something in the middle of the night for next day's reporting," said Steve Doherty, Linux systems manager at Cambridge Health. Whether a given file is stored on a solid-state drive will be determined automatically by 3PAR's T-Series Adaptive Optimization technology, he explained.

The 3PAR software's ability to handle these storage processes without heavy lifting by administrators is particularly welcome, Doherty said. "It's exceptionally easy to use. The intelligence of the software is one of the best things. You don't have to be a highly trained SAN administrator."

The ability to store data in a tiered fashion within a logical unit, or LUN, is known as sub-LUN granularity, according to Enterprise Strategy Group's Peters. The feature is supported by such competing vendors as Compellent Technologies Inc. and IBM, and storage giant EMC Corp. recently announced sub-LUN tiering for its Fully Automated Storage Tiering, or FAST, software.

Denver Health, meanwhile, uses thin provisioning for all the data it stores. "We don't want to drop a big volume out there and have it sit there not being used," said David Boone, the health care provider's operations and planning manager.

The hospital relies on LeftHand SAN/iQ Manager from Hewlett-Packard to forecast when it will need to add physical disk to the storage volumes. Microsoft System Center Operations Manager sends alerts about data volume requirements to IT administrators. "When it gets to within 10% of capacity, we add another," Boone said.

Denver Health implements tiered storage with iSCSI technology from Nexsan Corp. Once data meets certain criteria, it is migrated to second-tier storage, Boone said.

Replication eases pain of disaster recovery

Campbell Clinic, a Germantown, Tenn.-based health care provider specializing in orthopedics and sports medicine, saw the disaster recovery benefits of storage replication firsthand: When a rooftop cooling unit drain backed up, the server room flooded.

"This happened on a Friday at 5:10 p.m. We stayed until 10 p.m. that evening drying things out with fans. We lost a drive or two on the SAN and a [VMware] ESX server," said Peter Kim, IT manager at the clinic.

Campbell Clinic uses Dell Inc.'s EqualLogic SAN virtualized storage to create redundant disk arrays. When those disk drives were lost to water damage, the replicated SAN storage kicked in. "[By] Saturday at 2 p.m. we [had] brought up the environment," Kim said. "We couldn't have done that without virtual servers and storage. We had redundancy, so we failed over."

Cambridge Health relies on 3PAR for disaster recovery, in addition to using it for data storage and thin provisioning. "We're doing remote copy and syncing nearly all the time," LaPlante said. The network has a primary data center in a colocation facility and a separate disaster recovery site. All are within a 30-mile radius of headquarters; LaPlante declined to provide more specifics.

Data replication also came in handy when Cambridge Health moved to a new data center two years ago. In that case, remote copy tools copied data from one SAN to the other, Doherty said.

Replication is finding wide acceptance in health care, because hospitals often have large campuses or several buildings a mile or two apart, the Enterprise Strategy Group's Peters noted. "They could replicate from one building to another," he said.

Denver Health also benefits from replication. The institution maintains a total of 140 TB of data storage, half of which is replicated. Its two data centers (one at the hospital's main campus, the other 1.5 miles away at a secondary facility) each have two iSCSI Hewlett-Packard StorageWorks P4500 SANs. The locations are connected by 1 Gbps fiber links.

Using a triangular architecture, Denver Health can write data to SANs at either data center. The data is then replicated to the other location. Even if two SANs are down, according to Boone, the architecture's built-in redundancy prevents any drop in response time.

With lives hanging in the balance, hospitals like Denver Health can afford no less.

Stan Gibson is a Boston-based contributing writer. Let us know what you think about the story; email

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