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August 19, 2008

Panasas Broadens Storage Portfolio

by John E. West

Based in Fremont, Calif., and founded in 1999, Panasas is a privately held company that builds parallel clustered storage solutions. Although the company’s legacy is in traditional high performance computing installations, Panasas now realizes 80 percent of its revenue from the commercial side of its business, where companies like Statoil, PetroChina, Ferrari, and others in finance, bioinformatics, and various data-intensive industries are seeing a need for faster processing of large quantities of data. What all of these users have in common is that the amount of data they produce and store is growing dramatically as the amount of compute capability available to solve problems grows. A quick romp through the TOP500 confirms that yes indeed, the number of processors available at both ends of the list is growing quickly, and the resulting data has to be stored somewhere.

But the phrase “stored somewhere” hides many messy details. The data has to be written fast enough to avoid slowing the pace of an ongoing simulation or delaying other work from being done on a system. Likewise, data needs to be fed into the processors fast enough to keep them busy doing work, not waiting around for data. In both cases we need to be assured that what we are reading is what was written, and likewise for the reverse.

Large-scale storage has evolved from traditional single-server NFS architectures though clustered-NFS and onto parallel clustered storage, where we are today. The single- and clustered-server NFS solutions both put a file server on the path between the data source and the sink, an architectural constraint that ultimately limits the performance these solutions. The important feature of the parallel clustered approach is that it removes the file servers from the critical data path between the sink and the source, eliminating a key performance bottleneck. Panasas competes against commercial offerings from IBM, NetApp, and others, as well as open source projects like Lustre.

The industry is highly fragmented, and the high degree of proprietary technology and lack of interoperability that reflect the state of the practice in parallel storage may soon come to an end as the work to develop the parallel NFS (pNFS) standard comes to a conclusion. NFS version 4.1 is expected to incapsulate the new pNFS standard later this year, which Panasas is keenly anticipating. The company is committed to the evolution and adoption of pNFS as a catalyst for the storage industry.

“We firmly believe that the direction for storage and the direction for our business is into that broader scale-out marketplace with parallel storage,” says Matt Reid, Panasas’s director of marketing. “And one of the key enablers of this…is pNFS. Where we’re at today is that every parallel storage offering in the marketplace is proprietary, and pNFS will remove what is somewhat of an inhibitor to broader adoption, and enable parallel storage to progress into this much larger market.”

A parallel clustered file system removes some of the architectural impediments that limit the rate at which data flows between a source and sink, but there are plenty of other issues to be dealt with. One of the most interesting of these is also related to capacity — this time not in the amount of data that needs to be managed, but in the sizes of the drives on which it is stored. The storage industry has long been dominated by RAID, a technology first introduced in a 1988 paper co-authored by Garth Gibson, currently CTO of Panasas. A RAID 5 implementation stripes data across multiple disks, improving the speed of reads and writes, and stores metadata about what is written — called parity data — to enable recovery in the event that a single disk fails.

The approach protects data from many types of errors, but can’t help at all in the event that a read error occurs when rebuilding a lost disk. This will happen to about one in every 10^14 bits, or 12.5 TB. That wasn’t such a big deal when hard drives topped out at 50 GB. As drives pass 1 TB each in shelves of six, seven, or more drives, however, unrecoverable read errors during disk rebuilds are becoming a statistical certainty, virtually guaranteeing data loss or the need to recover slightly older data from much slower tape backups. RAID 6 can fix this problem when only one disk suffers an error during rebuild, but not more, and is thus only a partial solution.

To circumvent the problem, Panasas developed a “tiered parity” solution. Tiered parity generates a parity sector from other sectors on a disk that can be used to recompute missing data in the event of a media error. This new level of protection decreases unrecoverable read errors to 1 bit in 10^18 to 10^19, an improvement of 10,000 times in the best case. Although the original announcement was made during SC07, the technology hasn’t been released in final product form until today, with its inclusion in ActiveScale 3.2. For a more detailed treatment of tiered parity technology, see our October 2007 article on the topic.

The company has also announced three new hardware products. Two of them, the ActiveStor 6000 and ActiveStor 4000, are new releases of previous products (the ActiveStor 5000 and 3000, respectively). The ActiveStor 6000 is the high-end Panasas offering, aimed at large-scale design, modeling and data visualization. This solution incorporates the most software capability in the company’s offering and features 20, 15, or 10TB shelves, a 40 GB cache/shelf, and, for the first time, integrated 10 GbE. The capacity per shelf on the 6000 is the same as the previous 5000 series, but the new product features double the cache per shelf, and with 10 GbE the company is claiming data rates of 600 MB/second per shelf, nearly twice that of the 5000 products. The ActiveStor 4000, though still pretty beefy, is a lighter version of the 6000 designed for what the company sees as a simulation and analysis use case. The 4000 is missing some of its sibling’s software capabilities, though none of its performance, and again doubles the cache size of its 3000 series predecessor.

The third new product, the ActiveStor 200, is what Reid refers to as a “product family of one,” with a 104TB unit of sale. Like the ActiveStor 6000 and 4000, the solution features the company’s ActiveScale and PanFS software stack, but offers storage for secondary applications, like backup, where good (but not great) reliability is needed at a lower price point. The lower cost is evident in the performance tradeoff for the device. The 200 features five shelves, each with a single GbE port, offering an aggregate bandwidth of 350 MB/second for the entire system.

System cost is reflected in capability. The ActiveStor 200 is priced at around $1.2/GB, while the high-end 6000 series comes in at around $5.00/GB. The company characterizes the 4000′s price point as “between the 6000 and the 200, but closer to the 6000.” The ActiveStor 200 is available now, with two large installations in the UK. Panasas says it has “orders on the books” for both the 6000 and the 4000, with delivery scheduled next month.