Permabit

» see permabit.com as it lived, on the wayback machine

~ the obituary ~

The domain is still registered. A redirect sends permabit.com to redhat.com, onto the press release announcing that Red Hat has acquired the assets and technology of Permabit Technology Corporation. A dead company's domain pointed at its own obituary, 294 kilobytes of it, written by the buyer.

Permabit was started in 2000 by a technical and business team out of MIT, in Cambridge, Massachusetts, and it worked on one idea for its entire life. Storage is full of duplicates. The same virtual machine image sits on every host in a rack, and the same block turns up in a backup every night for a year. If you can recognize a block you have already seen, cheaply and fast enough to do it while the write is happening, you can keep one copy and hand out references. The hard part is the recognizing, at scale, without slowing the write down.

The first product shipped in 2004 under the name Permeon and was renamed Permabit Enterprise Archive: a multi-petabyte content-addressable store with write-once retention, aimed at the compliance archive market of that decade. In 2007 the company went through a management buyout, and the entity that came out of it, Permabit Technology Corporation, is the one that ended up in the Red Hat announcement ten years later.

Then it stopped selling boxes. From 2010 the business was Albireo, a family built around an in-memory hash index, licensed to the people who already sold storage rather than sold against them. Dell EMC, Hitachi, IBM and NetApp all shipped something with Permabit's deduplication inside it. The company's own name was on none of those products.

~ albireo ~

Albireo was packaged for whoever was buying. A hardware vendor could take the SDK and embed the index; a customer who wanted it finished could buy SANblox, a Fibre Channel appliance with the whole thing already wired up. The shape that mattered was the third one, VDO: a drop-in layer for Linux doing inline deduplication at a 4 kilobyte granularity, with compression and thin provisioning on top. Work on it started in 2009, four years before the first release.

~ drivers/md/dm-vdo ~

Red Hat announced the deal on 31 July 2017, for an undisclosed sum, and told investors it would not move the quarter's guidance. Sixteen Permabit people went across, among them founder and chief technology officer Jered Floyd and the vice president of product Louis Imershein. Red Hat's storage engineering sat in western Massachusetts and Permabit sat in Cambridge, so the team did not even have to move far. The announcement promised that the technology would be open-sourced, and that promise got kept.

Permabit did not leave a product behind. It left a directory. The code was released, maintained in the open for several years as an out-of-tree module, and on 13 March 2024 the device-mapper VDO target was merged for Linux 6.9. It lives at drivers/md/dm-vdo, it still does inline deduplication and compression, and the commit history on it continues under people who never worked for the company that started it in 2009.

There was never any way for me to meet this company. It sold petabyte archives to compliance departments and then sold an index to storage vendors, so the nearest thing to a consumer product was a feature bullet on an array nobody buys for a house. The one surface where its work could ever reach an ordinary engineer was a module name in a kernel tree, and a module name in a kernel tree is what it became. Permabit's name is on nothing anyone can buy, and its code now ships in the kernel whether or not anybody turns it on.

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