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Tape NAS emerges, utilizing LTFS for file access

Tape NAS brings file-level access to LTO tape for archiving, but Crossroads StrongBox is alone among hardware that takes full advantage of LTFS.

The concept of Linear Tape File Sytem (LTFS) has given rise to the term tape NAS because it provides the ability to access files on LTO tape as if they were on disk.

The first product to truly take advantage of this capability is Crossroads Systems’ StrongBox archiving appliance. According to Jon Toigo, a storage consultant, frequent contributor and tape advocate,  “The guy who wrote the book on [tape NAS] is Rob Sims at Crossroads Systems, who did the earliest designs I saw and who has created an elegantly integrated head with his StrongBox product. I have little doubt that other products will emerge in the market as this meme gains adherents.”

StrongBox offers a standard NAS interface, supporting NFS and CIFS. The appliance sits in front of a tape library and offers file-level access to the system using LTO-5 tape and LTFS.

“Tape has never really had file-based access, so if you wanted to do that type of activity disk was really your only option,” said Sims, who is Crossroads’ CEO. “LTFS is an answer to this at the technology level.”

One of the biggest challenges with long-term data retention is that previous versions of the software used to write to tapes is required to access the data. Sims said the combination of LTFS and NAS access allows data to be written to tape in a persistent format, ensuring data access from any platform going forward. 

“If you look at tiered storage, you have the memory-based, high-performance layer, [and] then you have a high-volume layer and then it kind of ends,” Sims said. “When it comes to long-term data retention, your only options are backup or agent-based HSM [hierarchical storage management] solutions.”

StrongBox comes in two versions: T1 offers 5.5 TB of cache, dual 6 Gb SAS ports or 8 Gb FC ports for connectivity to the tape library in a 1U form factor. Crossroads claims that this system offers support for up to 200 million files. The StrongBox T3 offers 14 TB of onboard cache, four 6 Gb SAS ports or 8 Gb FC ports for connectivity to the tape library in a 3U form factor. Crossroads claims that the T3 can support five billion files. Sims said users can expand capacity with additional external storage. 

While tape NAS is useful for storing large numbers of small files, Sims said most of the early StrongBox customers work in industries such as entertainment, video surveillance, or medical imaging. He said the Strongbox product is optimized for the big-file applications used in those industries.

When a large file such as a video is written to StrongBox, it is written directly to tape, but the first part of the file is also written to the appliance’s disk cache. When a user accesses the file, it is initially served from the disk cache. After that, the software locates and loads the appropriate tape into an available drive. Once the tape drive is positioned, StrongBox switches the read from disk to the tape path, serving the file directly from tape.

Accessed files are re-inflated to disk, allowing subsequent reads of the file to occur instantaneously from the file cache. Users can set policies around how long data should reside on the cache, what types of data get written to the cache, and how much of the file gets stored on the disk cache.

“If you have something like medical images and you need to store that data for a long time, the best media for that is tape. But you have to be able to get the files you need in a relatively short amount of time. Strongbox allows you to have an active archive using tape,” said David Hill, analyst with the Mesabi Group. “Right now the hot markets for [tape NAS are] the entertainment industry and medical imaging -- rich media stuff. But it can be used for all active archives. I think there are a lot of things it could be used for.”

Sims said Crossroads will add e-discovery functionality to StrongBox, but that is not an immediate concern for rich media.

“We are working with a partner to have a plug-in search engine for e-discovery,” Sims said. “But, we aren’t in any hurry, if we don’t have that solution out until this time next year that would be fine. We just haven’t seen any big push for that yet, but as we expand the business into other markets that will become an issue.”

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