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Another step in the Commodity Hardware Revolution

January 21, 2013 by Steve Modica

Steve Modica

Not too long ago, I was asked to write up my predictions on storage and networking technology for the coming year.  One of those predictions was the rise of new, combined file system/logical volume managers like ZFS and BtrFS.

These file systems don’t rely on RAID cards to handle things like parity calculations. They also don’t “hide” the underlying drives from the operating system. The entire IO subsystem – drives and controllers – is available to the operating system and data is laid out across the devices as necessary for best performance.

As we’ve begun experimenting ourselves with these technologies, we’ve seen a lot of very promising results.

First and foremost, I think it’s important to note that Small Tree engineers mostly came from SGI and Cray.  While working there, most of our time in support was spent “tuning.”  People wouldn’t buy SGIs or Crays simply to run a file server. Invariably, they were doing something new and different like simulating a jet fighter or rendering huge 3D databases to a screen in real-time.  There would always be some little tweak required to the OS to make it all work smoothly.  Maybe they didn’t have enough disk buffers or disk buffer headers.  Maybe they couldn’t create enough shared memory segments.

Small Tree (www.small-tree.com) has always brought this same skill set down to commodity hardware like SATA drives and RAID controllers, Ethernet networks and Intel CPUS. These days, all of this stuff has the capability to handle shared video editing, but quite often the systems aren’t tuned to support it.

I think ZFS is the next big step in moving very high-end distributed storage down into the commodity space

Consider this:  A typical RAID card is really an ASIC (Application Specific Integrated Circuit).  Essentially, some really smart engineering guys write hardware code (Verilog, VHDL) and create a chip that someone “prints” for them.  SGI had to do this with their special IO chips and HUB chips to build huge computers like the Columbia system.  Doing this is incredibly expensive and risky.  If the chip doesn’t work right in its first run, you have to respin and spend millions to do it again. It takes months.

A software based file system can be modified on the fly to quickly fix problems. It can evolve over time and integrate new OS features immediately, with little change to the underlying technology.

What excites me most about ZFS is we can now consider the idea of trading a very fast – and expensive – hardware ASIC for a distributed file system that uses more CPUS cores, more PCIE lanes and more system memory to achieve similar results. To date, with only vey basic tuning and system configuration changes, we’ve been able to achieve Titanium level performance using very similar hardware, but no RAID controller.

So does this mean we’re ready to roll out tomorrow without a RAID controller?

No.  There’s still a lot of work to do.  How does it handle fragmentation?  How does it handle mixed loads (read and write)?  How does it handle different codecs that might require hundreds of streams (like H.264) or huge codecs that require very fast streams (like 4K uncompressed)? We still have a lot of work to do to make sure ZFS is production ready, but our current experience is exciting and bodes well for the technology.

If you’d like to chat further about combined file system/logical volume managers, other storage/networking trends, or have questions regarding your workflow, contact info@small-tree.com.


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