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Supporting data-driven scientific research is always a challenge for storage managers. That's something that Timothy Belfield has discovered first-hand.

A senior technical analyst with the Donald Danforth Plant Science Center (DDPSC), in St. Louis, Belfield's team of four technical engineers has built and maintained a storage strategy to support the ever-increasing needs of some 200 researchers studying health-related plants, plant nutrition, disease resistance, novel bio-based products and tropical agricultural biotechnology.

Given the rapid growth in biotechnology research in recent years, data is being generated with increasing frequency and volume. What began as a modest amount of data at DDPSC's founding in 2001 has quickly blossomed into a full terabyte of data that's continuing to expand.

Data is stored on a storage area network (SAN) consisting of a 1.5TB Hewlett-Packard Co. (HP) StorageWorks Enterprise Modular Array 1200 system, three HP SAN switches, four HP HSG80 controllers, three HP MSL5026SL tape libraries, HP StorageWorks Modular Data Routers and 25 ProLiant DL380 servers. The environment includes a hodgepodge of operating systems and it supports business applications such as SQL Server 2000 and Exchange Server 2000.

Like most companies, DDPSC relies on tape to back up its critical data. But with data changing and growing so frequently, Belfield says, tape is struggling to keep up and has pushed the organization's backup window out to

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nearly four days. This is a constant source of frustration for the team, who would ideally like to see full backups completed in less than a weekend.

It's becoming increasingly clear that reaching their goal may never be possible using tape, and that is driving Belfield to consider alternatives.

"The amount of data we're backing up is growing, growing, growing, and our backup window is growing daily," he says. "For us, tape is the best now, but we never know exactly what we should be looking for in speed. If we can't get the backup window to come down, we'd have to look at disk. IDE disks would be a little slower than SCSI, but a lot faster than tape."

Although its primacy as a backup medium was unchallenged for decades, the plummeting cost of disk drives and the sheer bulk of data now being backed up in the average business have highlighted tape's major weakness: It's a slow backup medium. Each generation of tape technology provides faster performance, but those tapes still work the same way--by physically moving the tape past a read/write head with either linear or helical data streams.

This makes tape use a heavily mechanical process that still depends on getting a constant stream of information from the servers it's backing up. In today's high-performance network-attached storage (NAS) and SAN environments, ensuring this exclusive access can be downright difficult. It's an issue that quickly leads to tape problems as networks become flooded with backup data and tape performance slows, thanks to undue numbers of tape rewinds. "You're constantly fighting with tape and the drive itself," says Belfield. And those problems just refer to backup--not restores.


Tape road maps
TECHNOLOGY DATA CAPACITY NATIVE/COMPRESSED TRANSFER SPEED NATIVE/COMPRESSED WHEN TAPE SIZE DUTY CYCLE
LTO Ultrium Generation 1 100GB/200GB 15/30MB/s 2001 1/2"  
LTO Ultrium Generation 2 200GB/400GB 35/70MB/s Now    
LTO Ultrium Generation 3 400GB/800GB 80/160MB/s      
LTO Ultrium Generation 4 800GB/1.6TB 160/320MB/s      
AIT-1 35GB 3/6MB/s 2001 1/2"  
AIT-2 50GB/130GB 6/15.6MB/s      
AIT-3 100GB/260GB 12/31.2MB/s Now    
SAIT-1 500GB/1.3TB 78/300MB/s Late 2003    
DLT1 40GB 3MB/s Now 8mm  
DLT 7000 35GB/70GB 5/10MB/s Now    
DLT 8000 40GB/80GB 6/12MB/s Now    
Super DLT 220 110GB/220GB 10/20MB/s 2001    
Super DLT 320 160GB/320GB 16/32MB/s Now    
Exabyte Mammoth 2 60GB 12MB/s Now    
DDS-4 20GB 3MB/s Obsolete 4mm 20%
Travan NS 10GB 1MB/s Obsolete   20%

This was first published in September 2003

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