Store more with less
Storage disk arrays put high capacities and fast speeds into small spaces
- By Edmund X. DeJesus
- Aug 21, 2008
Every agency faces a similar storage challenge: Store more data in a smaller space while keeping it easily accessible. Disk arrays provide one way to solve that puzzle.
At its most basic, a storage disk array is simply a collection of multiple disk drives with cache memory, controllers, power supplies and other supporting hardware. The current generation of arrays also offers a smorgasbord of speed, capacity, data-protection, security, replication and space-saving tricks. And many products offer savings in power and cooling ' important considerations given the surging cost of energy and increasing mandates for green computing.
At the same time, the space needed to accommodate disk arrays is shrinking. 'You can now double, triple or quadruple your data capacity in the same footprint using less energy,' said Greg Schulz, founder and senior analyst at StorageIO Group, a consulting firm.
Finally, many government agencies are trying to satisfy multiple requirements. In some cases, retrieval speed is critical. In other situations, particularly when data is stored online, drive speed might be less important because users' Internet connections will determine how quickly they can access files. In those cases, agencies might want to trade disk speed for smaller size, lower power, better cooling or lower cost.
In selecting a disk array, 'don't focus on acquisition cost as much as on what you're trying to achieve,' said R.B. Hooks, chief technology officer of the Storage Group at Sun Microsystems Federal.
Naturally, every advance in hard-drive technology finds its way into storage arrays, and new developments in technical protocols help disk arrays provide data more easily.
There's a trend toward functional convergence, with Fibre Channel and Internet SCSI drives, Common Internet File System and Network File System drives, and Fibre Attached Technology Adapted and Serial Advanced Technology Attachment drives, said Andrew Reichman, a senior analyst at Forrester Research.
In other words, agencies have plenty of options for meeting their objectives.
Want to shrink your data centers? Use high-capacity drives. Need to speed access to data? Get the fastest ones. Want to save money? Avoid the biggest and speediest models and go for the next-lowest tier of perfectly capable drives.
Most disk arrays use some form of Redundant Array of Independent Disks technology, which achieves higher reliability than a single disk by distributing data across two or more physical drives. Also, the technology allows the disks to send data faster than individual drives can.
Consolidating resources is a primary goal of many agencies and departments, partly to reduce costs and partly to simplify management.
'Customers often want fewer data centers ' or just one,' said Kyle Fitze, director of marketing at Hewlett-Packard's Storage Platforms Division. Given the prevalence of concentrated storage, consolidation has become not only feasible but also fairly easy. Reduction strategies
Lean provisioning is one strategy for doing more with less. Systems often allot too much space to applications, which can waste resources. Rather than reserving storage space for an application or server, lean provisioning makes that space reservation conditional. For example, if two applications each supposedly require 10T, lean provisioning would grant each one only 6T, with perhaps another 4T in reserve. Odds are, those applications will be completely content with their lean rations, and the system will have space for other needs.
How likely is lean provisioning to help your organization? It depends on your applications, data and operating system.
'Typically, Windows has 25 to 30 percent usage, Unix has 35 to 45 percent usage and mainframes about 80 percent usage,' Hooks said. That leaves a lot of wasted space.
Vendors implement lean provisioning in various ways. For example, Sun offers the StorageTek 9900 Software Suite for virtualization and dynamic provisioning and the Solaris ZFS 128-bit file system, which doesn't consume storage until data is written.
Another strategy for minimizing storage use is data deduplication, which reduces or eliminates redundant information. For example, if you send an e-mail with an attachment to a co-worker, there are now two copies of that attachment. Rather than store both copies, deduplication tools store only one and point to that one copy for all other references.
'While common in backup systems, deduplication is now in primary systems,' Reichman said. The technology saves space and bandwidth needed to move that data around.
In addition, data compression can reduce the raw size of stored files. The savings in storage depends on the kind of data being compressed. Many image files have already been compressed as much as they can be, but text documents and databases can often be compressed by 80 percent.
Another common strategy is tiered storage, in which different tiers of disks are used for different purposes: Your fastest disk is for data that must be accessed quickly, while less speedy disks are for data that's not so urgent.
'You can set the rules for which data belongs on which tier,' said Mark Peters, an analyst at Enterprise Strategy Group.
Some disk arrays can even make those adjustments automatically. For example, Compellent Technologies' products assign data to drives dynamically based on usage and thereby lower management and administration costs. Protecting data
Most agencies are required to maintain backups of their files, preferably at another location. Many hard-drive arrays perform that replication automatically.
'The idea is disaster avoidance without disruption, not disaster recovery,' Schulz said.
Unfortunately, agencies often find out that their disaster recovery plans don't work when it's too late. For example, Charlotte County, Fla., officials had to physically move servers to a safe location during 2004's Hurricane Charley.
'Many of our servers were running without air conditioning, which is not ideal,' said Mark Ramsey, the county's IT operations manager.
Securing data is as important as backing it up. Accordingly, some disk arrays now offer the option of encrypting every piece of data and digitally shredding it if a drive is removed without authorization.
'This can help any agency with issues of compliance or chain of custody,' said Dave Egan, senior vice president of storage at Fujitsu Computer Systems.
DriveTrust technology ' a joint effort by Advanced Micro Devices, HP, IBM, Intel, Microsoft, Seagate Technology and Sun ' features firmware that encrypts drives and enables secure erasure. In addition, manufacturers such as EMC and Fujitsu offer encrypted drives.
However, if you choose drive encryption, invest in specialized software that keeps track of encryption keys so you don't have to. Eye on the future
To facilitate future needs for expansion, consider vendors that offer compatible disk arrays at different levels of storage.
Fortunately, transmission protocols are also changing. The hot one these days is Fibre Channel over Ethernet (FCOE). Many data centers already use Ethernet for their TCP/IP networks and Fibre Channel for their storage- area networks. By adopting FCOE, agencies can run Fibre Channel traffic over their Ethernet connections without the need for special Fibre Channel cabling or for the less-well-known iSCSI protocol.
'This simplifies implementation because most staff [members] are already familiar with Ethernet,' Peters said.
For those who need super-fast mass storage, solid-state flash memory is now available in hundreds of gigabytes. Granted, it isn't a harddrive array, but if you need to store large amounts of data for rapid access, flash memory drives can be useful.
Regardless of your needs, remember that hard-drive prices keep dropping even as speed and capacity increase, which is why you shouldn't rush your decision.
'Don't buy storage until you need it,' Hooks said.