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What Storage Costs

With discount computer stores selling disk drives for a dollar per gigabyte, how can enterprise storage systems cost many times that amount? Fry's electronics, for example, recently advertised the Buffalo TeraStation at $1699 for 2 TB of NAS. That's $1.17 per GB.

"We charge the equivalent of around $252 per GB for high-end Fibre Channel RAID," says James Yaple, IT specialist at the Austin Automation Center of the U.S. Department of Veteran's Affairs.

He breaks that down as $7 per GB per month spread over three years. That's the rate he charges other government units for storage on demand. Some customers see it as an acceptable rate, while others are driven to look elsewhere for cheaper storage that they attempt to manage locally. In Yaple's mind, however, the cost of storage goes way beyond raw GB numbers.

“How much is your data actually worth?”

— James Yaple

"How much is your data actually worth?" Yaple asks. "When you are dealing with confidential information or healthcare records, sometimes low cost isn't what you need or want."

Low cost, he says, comes at a price — greater risk, lower performance and lower reliability. The quality you pay for shows up in areas such as better physical connectors, hot swap features, redundancy, maintenance agreements, RAID, higher performance, heterogeneous support and remote management/alerting. At the higher end, you can add in functions such as remote mirroring and capacity on demand. Some arrays from EMC, for example, have TimeFinder built in for additional snapshot capabilities.

Thus, the $7 per month rate includes a mirrored pair and RAID 1 or 1+0. To replicate disks to an alternate location, it costs $23 per GB per month.

"Those that try to buy their own storage may think it's cheaper, but they don't take into account the storage administrative costs, which are bundled into our rates," says Yaple.

That said, the VA is moving away from one-size fits all storage. It is building a tiered structure with common elements for each tier such as RAID 1/5 or 0+1, security (LUN masking, central management) and SMI-S conformance.

The Basic Tier will hold a minimum of 5 TB and meet certain benchmarks for a targeted cost of less than $10/GB per month. These benchmarks are based on the Storage Performance Council (SPC) model: 100 I/O per sec minimum for the host on the SPC-1 benchmark and an average throughput of 10 MBPS on the SPC-2 benchmark.

In the mid-tier, the VA is targeting a cost of $20 per GB for 50 TB of storage that meets 250 IOPS on SPC-1 and 25 MBPS on SPC-2. For its premium tier, the VA intends to keep the costs under $125 per GB per month for 50 TB of storage that offers 500 IOPS on SPC-1 and 25 MBPS on SPC-2.

"We will use the workload characteristics to determine which tier," says Yaple. "As well as average MBPS, we are also using peak MBPS as a valuable metric."

Benchmarking RAID Performance

To assist with this, he is also making use of the Oracle I/O Numbers (ORION) benchmarking tool, which is available as a free download from the Oracle site. It helps the VA to see what performance and throughput it gets from different storage tiers and types of disk when using an Oracle database.

Yaple used Orion, for example, to test an Apple Xserve RAID box containing 14 500GB ATA drives. It was hooked up to a Dell PT 2650 server with dual Emulex 9000 HBAs. He liked the potential of the Xserve box, but decided to test it first to see if this kind of low-cost storage would be suitable for his environment.

The ORION tests showed that various factors and configurations affected results. RAID, for example, changed the results significantly.

"We saw double the performance from RAID 0+1 compared to RAID 5," says Yaple. "So now we tell customers that if they want performance, they should opt for RAID 0+1."

He also notes that the various RAID levels have a dramatic impact on available storage, and therefore cost per GB. Per his calculations, just a bunch of disks (JBOD) would cost $6.14/GB, whereas RAID 5 would cost $7.17. RAID 0+1, on the other hand, raises the total to $14.34.

“What makes storage cost so much is performance and the degree of protection.”

— James Yaple

His conclusion?

"What makes storage cost so much is performance and the degree of protection," says Yaple.

In the case of Apple Xserve RAID, he found that it was particularly good at large I/Os. Unfortunately, that wasn't what he needed it for. So the Apple box has yet to find a place at the VA's Austin Automation Center.

Article courtesy of Enterprise IT Planet



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