Was SAN File System really five years ahead of its time?
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Fellow master inventor and blogger Barry Whyte (IBM) recounts the past 20 years of history in IT storage from his perspective in a series of blog posts. They are certainly worth a read:
In his last post in this series, he mentions that the amazingly successful IBM SAN Volume Controller was part of a set of projects:
"IBM was looking for "new horizon" projects to fund at the time, and three such projects were proposed and created the "Storage Software Group". Those three projects became know externally as TPC, (TotalStorage Productivity Center), SanFS (SAN File System - oh how this was just 5 years too early) and SVC (SAN Volume Controller). The fact that two out of the three of them still exist today is actually pretty good. All of these products came out of research, and its a sad state of affairs when research teams are measured against the percentage of the projects they work on, versus those that turn into revenue generating streams."
But this raises the question: Was SAN File System just five years too early?
IBM classifies products into three "horizons"; Horizon-1 for well-established mature products, Horizon-2 was for recently launched products, and Horizon-3 was for emerging business opportunities (EBO). Since I had some involvement with these other projects, I thought I would help fill out some of this history from my perspective.
Back in 2000, IBM executive [Linda Sanford] was in charge of IBM storage business and presented that IBM Research was working on the concept of "Storage Tank" which would hold Petabytes of data accessible to mainframes and distributed servers.
In 2001, I was the lead architect of DFSMS for the IBM z/OS operating system for mainframes, and was asked to be lead architect for the new "Horizon 3" project to be called IBM TotalStorage Productivity Center (TPC), which has since been renamed to IBM Tivoli Storage Productivity Center.
In 2002, I was asked to lead a team to port the "SANfs client" for SAN File System from Linux-x86 over to Linux on System z. How easy or difficult to port any code depends on how well it was written with the intent to be ported, and porting the "proof-of-concept" level code proved a bit too challenging for my team of relative new-hires. Once code written by research scientists is sufficiently complete to demonstrate proof of concept, it should be entirely discarded and written from scratch by professional software engineers that follow proper development and documentation procedures. We reminded management of this, and they decided not to make the necessary investment to add Linux on System z as a supported operating system for SAN file system.
In 2003, IBM launched Productivity Center, SAN File System and SAN Volume Controller. These would be lumped together with Horizon-1 product IBM Tivoli Storage Manager and the four products were promoted together as the inap
The SAN File System was the productized version of the "Storage Tank" research project. While the SAN Volume Controller used industry standard Fibre Channel Protocol (FCP) to allow support of a variety of operating system clients, the SAN File System required an installed "client" that was only available initially on AIX and Linux-x86. In keeping with the "open" concept, an "open source reference client" was made available so that the folks at Hewlett-Packard, Sun Microsystems and Microsoft could port this over to their respective HP-UX, Solaris and Windows operating systems. Not surprisingly, none were willing to voluntarily add yet another file system to their testing efforts.
Barry argues that SANfs was five years ahead of its time. SAN File System tried to bring policy-based management for information, which has been part of DFSMS for z/OS since the 1980s, over to distributed operating systems. The problem is that mainframe people who understand and appreciate the benefits of policy-based management already had it, and non-mainframe couldn't understand the benefits of something they have managed to survive without.
(Every time I see VMware presented as a new or clever idea, I have to remind people that this x86-based hypervisor basically implements the mainframe concept of server virtualization introduced by IBM in the 1970s. IBM is the leading reseller of VMware, and supports other server virtualization solutions including Linux KVM, Xen, Hyper-V and PowerVM.)
To address the various concerns about SAN File System, the proof-of-concept code from IBM Research was withdrawn from marketing, and new fresh code implementing these concepts were integrated into IBM's existing General Parallel File System (GPFS). This software would then be packaged with a server hardware cluster, exporting global file spaces with broad operating system reach. Initially offered as IBM Scale-out File Services (SoFS) service offering, this was later re-packaged as an appliance, the IBM Scale-Out Network Attached Storage (SONAS) product, and as IBM Smart Business Storage Cloud (SBSC) cloud storage offering. These now offer clustered NAS storage using the industry standard NFS and CIFS clients that nearly all operating systems already have.
Today, these former Horizon-1 products are now Horizon-2 and Horizon-3. They have evolved. Tivoli Storage Productivity Center, GPFS and SAN Volume Controller are all market leaders in their respective areas.