Online marketer Pentius has evolved from an iSCSI SAN to server-side flash as cache for data analytics storage....
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The last piece of the picture was PernixData's Flash Virtualization Platform (FVP) software, which accelerates flash reads and writes and reduces latency.
Earlier this year, Pentius installed the clustering software to virtualize flash and RAM resources for its hybrid SQL Server environment. PernixData FVP stores high-availability applications in flash cache -- specifically 1.2 TB SLC ioDrive 2 Duo cards from flash vendor Fusion-io, which is now part of SanDisk. Any server that runs PernixData FVP can access flash on any other server in the cluster.
"Using FVP with the Fusion-io cards has taken about 95 percent of reads off our SAN, which is almost never used for a read operation now," said Pentius CTO Martin Toha. "The other thing is, those reads are returned much quicker because they're coming from the local host off of the flash storage."
High input/output operations per second is a key driver for Pentius, which provides online marketing tools that help financial services companies acquire customers and build brand loyalty. Pentius uses search marketing, online ads and affiliate marketing to drive traffic to its customers' websites.
Pentius keeps tabs on metrics for display ads and media buys, and monitors customer-acquisition initiatives to determine if they are producing the desired results. The company uses Microsoft SQL Server for its online transactional processing workload (OLTP). It licensed SQL Server 2014 shortly after it was rolled out in April and plans to gradually move data from earlier SQL versions to the new system. Pentius also runs Windows Server 2012 R2 and several versions of Linux, along with 150 virtual machines running VMware's ESXi hypervisor.
Pentius has an iSCSI SAN composed of Dell EqualLogic PS6500 Series arrays with a 10 Gb Ethernet backplane. Toha said the SAN is adequate for applications that don't require rapid access or high availability, such as non-analytic file data. Over time, Pentius maxed out its random access memory (RAM), yet still had too much latency for SQL reads and writes coming off the SAN.
Pentius still uses the EqualLogic for its VMware storage but not for SQL.
"The EqualLogic could only give us 1,000 to 2,000 IOPS and after that, we were really suffering. So, if you wanted to do backups on top of replication on top of OLTP, forget it," Toha said.
That dilemma prompted Toha several years ago to explore solid-state storage as an option to replace the EqualLogic stack. At that time, the price for flash drives was much more expensive than it is now, Toha said, so he started in 2011 with a small deployment of lower-end Fusion-io PCIe cards for temporary database operations and queries.
As the flash cards filled up, Toha faced a dilemma: purchase more expensive flash storage or sink money into upgrading the HDD-configured SAN. Besides cost, flash presented challenges. Using PCIe cards as persistent disk limits storage to its physical host, but Pentius needed multi-point availability. And, although it never happened, Toha worried that one day a flash card would wear out, taking revenue-generating data with it.
"It got to the point two years ago where we knew we could not run the SQL database on spinning disk, and I was tired of worrying we would lose a flash card," Toha said.
Adding to the complexity is Pentius' highly virtualized environment, which includes replication between virtual machines. Virtualization has some drawbacks with respect to SQL Server performance, but Toha said he "gave up on bare metal some years ago."
The PernixData FVP software has removed the headaches of having to stage and classify storage, Toha said, although he had doubts in the beginning. "With our old regime, we told the storage, 'This data goes in flash, this other data goes to the SAN,'" he said. "The concern was that Pernix wasn't going to be smart enough to figure that all out, but it is."
PernixData enables Pentius to scale by adding more flash as needed. Toha said he's impressed by the FVP algorithm.
"You might know you have 20 TB that demands 20,000 IOPS, but you might not know that only 1 TB is using 19,500 IOPS and the other 19 TB are using nothing," he said. "What's nice about Pernix is it gets to the bottom of that and only caches in flash what needs to be cached in flash. It's like having a storage array where I can control the amount of flash in the flash tier and do it on the fly."
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