The more you spend, the more you save. That's what some IT managers find when, in their effort to improve I/O performance,
they install expensive solid-state disk (SSD) technology in servers.
Last year the reference website Answers.com began to experience I/O performance bottlenecks on its database servers, which were Hewlett-Packard Co. BladeSystem ProLiant Server Blades. Answers.com runs the MySQL databased and configures each cluster with a master database server, plus a farm of read-only, synchronized database slaves that handle the bulk of queries.
As the site grew and received more updates, it became difficult for these slaves to serve incoming requests quickly -- and handle the replication updates coming from the master -- and response times were taking a hit.
Tackling I/O issues with SSD technology
Usually, the solution to I/O problems is to connect servers to storage arrays configured with lots and lots of spinning hard-disk drives, "but that's not very economical to house and maintain and to pay for in terms of power consumption," said Dan Marriott, the director of production operations at Answers.com.
Less hardware equals less failure.
director of production operationsAnswers.com
Nor could the firm simply add more nodes to its clusters.
"We can't buy unlimited servers; we have realistic hardware budgets," Marriott said.
Instead, Answers.com tried to put SSD technology in the slave servers. The company moved the database copy from internal disk drives to a 320 GB HP StorageWorks IO Accelerator, a NAND flash-based storage adapter that HP OEMs from Fusion-io, and replication recovery time decreased from 6 hours to 12.5 minutes, Marriott said.
ROI from SSD technology
In addition, the flash drive boosted the number of complex queries the servers could perform from 350 per second to 3,500 per second, and it improved application response time by 30%. That in turn allowed Answers.com to reduce the number of servers in each database read cluster from 20 down to five, for a net cost savings.
Even though the IO Accelerator cards cost about twice as much as an individual server, "we got immediate [return on investment]," Marriott said. Using approximate numbers, given a typical database cluster with 20 $5,000 servers, the company equipped five servers with a $10,000 flash drive, for a cost of $50,000, and repurposed the remaining 15 servers for a savings of $75,000.
"Deploying these Fusion-io cards actually saved us $25,000 in Capex for each of our database clusters, right off the bat," Marriott said.
Beyond that, Answers.com enjoys improved operational savings from the reduced number of servers, including admin time, space in its racks, power and cooling, and fewer points of failure, Marriott said.
"Less hardware equals less failure," he said.
Installing the card and its driver is "trivial," Marriott said. "It's the simplest thing; you just add the mezzanine card, which takes about 60 seconds. Then you reboot the server, install the driver, format the drive, then you copy your data across, and away you go."
SSD technology en masse
Of course, using Flash to improve performance is nothing new, but the use of SSDs in the enterprise is on the rise, said Jeff Janukowicz, IDC's research manager for SSDs. It's still an early market, but IDC expects that between now and 2014, shipments of enterprise SSDs will grow by 75%, he said.
IDC attributes SSD's growth in the enterprise to two factors: decreasing cost and the rise of multicore processors. Over the past decade, the price of NAND memory decreased by 50% per year, Janukowicz said. On a dollar-per-gigabyte basis, SSDs still cost about 28 times that of traditional hard disk drives, but IDC expects that number to continue to drop.
"We don't anticipate that SSD will ever be cheaper than hard disk drives, but that's not really necessary," Janukowicz said. "It's more about leveraging SSDs for what they can bring to the system."
At the same time, faster microprocessors have an increased thirst for fast storage subsystems.
"Moore's Law and recent advancements in processor power have put pressure on storage subsystems to keep the processor filled with data," Janukowicz said.
Fusion-io's SSD-on-PCIe adapter card is but one variation on the enterprise SSD theme. SSD is often integrated into traditional storage arrays, such as EMC's FAST, as a high-speed storage tier. On the device side, STEC, Pliant Technologies and other companies create serial-attached SCSCI (or SAS) drives based on SSD, and traditional hard disk drive manufacturers such as Seagate have also gotten in on the act. Finally, Violin Memory Inc. and Texas Memory Systems Inc. are among the companies that offer entire storage arrays created from SSD.
The real challenge is identifying which applications can make effective use of SSD technology, Janukowicz said. Workloads that are good candidates for SSDs include databases, online transaction processing, streaming video on demand and even virtual desktop infrastructure.
"In general, any workload that is I/O-intensive, those are the ones that will benefit the most," Janukowicz said.
Write-intensive applications, meanwhile, may or may not benefit from SSDs, Marriott said. But generally speaking, "if you're seeing performance problems because of I/O limits, there's a pretty good chance that Fusion-io or other enterprise-grade SSDs can be a game changer."