April 28, 2010

Active Archives: A Way to Tame the Data Monster

by Michael Feldman

It seems like every information technology has its own industry trade group these days. The latest one to join the herd is the Active Archive Alliance, a group dedicated to pushing active archive solutions into the mainstream. The Alliance was announced this week with its founding members Compellent Technologies, FileTek, QStar Technologies, and Spectra Logic.

According to the latest IDC numbers, external storage is growing at an annual rate of 58 percent and estimated to reach a whopping 1610 exabytes by 2011. As a result, companies are scrambling to find places to keep their data, and keep it accessible. This is certainly true in HPC, where the size of datasets is growing in parallel with the computational power of supercomputers. In the enterprise, storage growth is just as epidemic. Between email, structured data of all types, multimedia files, and regulations that mandate new storage requirements, organizations are being overwhelmed.

The result is that datacenters are turning into spinning disk warehouses, with storage infrastructure gobbling up floor space, power, and IT budgets. One saving grace is that most of the data on primary storage — perhaps as much as 75 to 85 percent of it — does not need to be accessed frequently. That suggests that much of the data currently sitting on high-end disk drives can be migrated to much denser, less expensive, and less power-hungry storage systems. And that’s where active archives come in.

The definition of an active archive is a little fluid, but the Alliance defines it as a storage system that contains production data, no matter how old or infrequently accessed, that can still be retrieved online. Essentially, it’s a storage tier than sits between offline backup and primary storage. It could be based on tape or disk, but in either case the archive should be accessible through a file system, like NFS or CIFS.

It’s this last feature that is at the center of the value proposition for active archives. Mounting a file system atop such a solution makes file access transparent to users, scripts, and applications. And even if access times are greater than the millisecond-level response you get from primary storage, the underlying software and the interface is still the same.

File systems, of course, are old technology, but not in the archive arena, especially for tape-based systems. “What is new is that there are applications now available that can extend the file system to tape, whereas historically file systems have relied on disk technologies,” explains Molly Rector, vice president of marketing and product management at storage vendor Spectra Logic.

Spectra is one of the four founding members of the Active Archive Alliance and is positioning itself as the premier vendor for active archive solutions in the tape storage domain. Rector says a tape library five to 10 years ago would not have been an appropriate solution for this application, but scalability, performance, and reliability and data integrity have advanced to the point where tape-based active archives are now commercially viable.

The large HPC labs have actually been at the forefront of this technology and are leading the charge on archive tape libraries with a file system front-end. NASA Ames, for example, installed two Spectra tape libraries and increased its active archive storage capacity from 12 PB to 32 PB, recouping 1,400 square feet of datacenter space in the process. The future (2011) Blue Waters supercomputer at NCSA is also slated to include a 500 PB tape archive, fronted by a GPFS-HPSS interface.

But according to Rector, most other industries, and the majority of HPC users, are not even aware that such a capability exists. The Alliance’s mission is to drive these solutions into the mainstream datacenter, and not just for petabyte-sized datasets either. There are plenty of organizations with terabytes of infrequently accessed files, but who have run out of room on their primary storage. In genomic research environments, for example, raw genetic data is being accumulated at a rate that outpaces any reasonable NAS or SAN deployment scheme. Since much of this data is not in constant use, it would seem to be an ideal app for a tape-based archive.

Archives are not just the tale of the tape, however. The other founding Alliance members — Compellent Technologies, FileTek, and QStar Technologies — offer a mix of disk-based and tape-based archiving solutions. Even Spectra has a disk-based product set, although for now the company is focused on its tape-based offerings for active archives. Panasas, although not part of the Alliance, recently launched, PAS HC, its disk-based NAS solution for archiving and scratch storage.

Choosing between a disk-based or tape-based archive comes down to how fast you need to get at your file. In general, online tape access can run anywhere from one to several minutes, while disk archives usually can deliver a file within a few seconds. (This is substantially different from offline tape backups, which can take hours, or even days to retrieve a file.) The slower access time of tape is offset by its greater storage density and power efficiency — and in both cases, orders of magnitude greater. Media cost is also much better for tape, which tends to run about $40 per terabyte. For cheap SATA or SAS disks, it’s more like $70 per terabyte, and for enterprise Fibre Channel and SAS, $150 per terabyte.

In a perfect world, you would only have to choose a single archive media, but in the real-world, the optimal solution will probably involve a two-tiered disk-tape infrastructure. Spectra’s Rector thinks an 80/20 tape/disk split might be optimal ratio to balance cost, access performance and storage density. Disk-centric vendors like Panasas might think differently, of course.

For the time being, the Alliance will work to add more members, define the market, develop best practices, and just generally educate the user community about the value of active archive solutions. Over the next several months, the group will be generating webinars and white papers as well as showing up at the appropriate trade shows. Beyond that, once a critical mass of customers has adopted the technology, expect to see the formation of a users group.

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