Other articles

  1. Winter Running in New England

    Fri 09 October 2015

    tags: running

    I still consider myself a bit of a running n00b. Several months ago, I was even more of one - so much so that I kept running through one of the worst winters anyone here seems able to remember. Paradoxically, that n00b decision seems to have left me in the position ...

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  2. A Year Of Running

    About a year ago, I started running. I say "about" a year because I don't know the exact date. I know it was early July, so it's not quite a year, but I feel like writing about it now so here goes.

    A year ago, I knew nothing ...

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  3. Object Store File Systems

    Several years ago, Amazon created something called S3 - Simple Storage Service. The "simple" part was based on the premise that distributed file systems are too complex, inhibiting scalability while providing too little marginal value to users. According to that theory, a system with a simpler API and semantics (e.g ...

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  4. Distributed File System SBFAQ

    There's a lot of hype around distributed file systems and their relatives, such as object stores. Every week, it seems, there's a new project claiming to be the the fastest, most scalable, most robust, most space-efficient distributed file system ever, sweeping all precursors before it. Nine times out ...

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  5. Stop Calling It Neutrality

    Usually, when anyone in government tries to do anything about issues of equality or fairness, the techie-libertarian reaction is to complain about "legislating equal outcomes" and invoke the spectre of Harrison Bergeron as proof. (Hint: it's fiction!) For some reason, "neutrality" doesn't get the same reaction even though ...

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  6. Content From hekafs.org

    Executive summary: all of that stuff's over here now. If you have links to it, just change "http://hekafs.org" to "http://pl.atyp.us/hekafs.org" and almost everything should work.

    A while ago, I got a notice that the hekafs.org domain was about to expire. Even ...

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  7. Life on the Server Side

    Of all the projects I've proposed or worked on for GlusterFS, New Style Replication (NSR) is one of the most ambitious. It has two major goals:

    • Improved handling of network partitions

    • Improved performance, both normally and during repair

    Personally, I consider the improved partition handling to be the more ...

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  8. How Erasure Coding is Not Like Replication

    Fri 13 February 2015

    tags: storage

    Many people think of erasure coding as equivalent to replication, but with better storage utilization. Want to store 100TB of data with two-failure survivability? With replication you'll need 300TB of physical storage; with 8+2 erasure coding you'll need only 125TB. Yeah, sure, there's a performance downside ...

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  9. Notes on File System Semantics

    Fri 09 January 2015

    tags: storage

    Just some random thoughts from an email I sent recently, plus a bonus SCSI war story.

    As the PVFS folks said long before I came along, some POSIX requirements are inappropriate for a distributed file system. I agree with that, but not with the object-store folks who claim that the ...

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  10. Technical Debt vs. Technical Risk

    One of the most useful metaphors in software engineering is Ward Cunningham's technical debt. Definitions and interpretations vary, but technical debt is basically all the stuff you're going to fix later because you were in too much of a hurry to do it right the first time. We ...

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  11. Why "DSO" is an Awful Term

    A recent discussion on the GlusterFS development mailing list got a bit hung up on the issue of what is or is not a "DSO" (Dynamically Shared Object). This is one of a many issues with dynamic linking and dynamic loading that I've seen cause problems before, in large ...

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  12. "Scale Out" Applies to Interfaces, Too

    Wed 03 December 2014

    tags: design

    Because of what I do for $dayjob, I hear a lot about "scale out" vs. "scale up" in various contexts. Also because of what I do for $dayjob, I get to read a lot of code. Some of it's new and clean. Some of it's . . . not. That's ...

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  13. Thoughts on Running

    Tue 21 October 2014

    tags: running

    (...and now for something completely different.)

    Back in July, I started running. That would not be a particularly notable statement for many people, but most people haven't detested running all their lives and avoided it for thirty years. Instead, I've used stairclimbers and ellipticals for many years, but ...

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  14. Distributed Systems Prayer

    Forgive me, Lord, for I have sinned.

    • I have written distributed systems in languages prone to race conditions and memory leaks.

    • I have failed to use model checking when I should have.

    • I have failed to use static analysis when I should have.

    • I have failed to write tests that ...

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  15. Ten Stages of Technology Familiarity

    Wed 10 September 2014

    tags: humor

    Without further ado...

    1. Never heard of it.

    2. Yeah, I hear all the hipsters yammering about it.

    3. I checked out the docs and examples once.

    4. I used it for a side project.

    5. We're using it for some new projects at work.

    6. We're using it in production.

    7. We're using ...

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  16. Wannabe of the Month: Skylable

    Every month or two, someone comes along and claims to be the new Best Thing Ever in distributed file storage. More often than not, it's just another programmer who recently discovered things like consistent hashing and replication, then slapped together another HTTP object store because that's what people ...

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  17. Inktank Acquisition

    I know a lot of people are going to be asking me about Red Hat's acquisition of Inktank, so I've decided to collect some thoughts on the subject. The very very simple version is that I'm delighted. Occasional sniping back and forth notwithstanding, I've always been ...

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  18. New Style Replication

    This afternoon, I'll be giving a talk about (among other things) my current project at work - New Style Replication. For those who don't happen to be at Red Hat Summit, here's some information about why, what, how, and so on.

    First, why. I'm all out of ...

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  19. Change the Axis

    The other day, I was talking to a colleague about the debate within OpenStack about whether to chase Amazon's AWS (what another colleague called the "failed Eucalyptus strategy") or forge its own path. It reminded me of an idea that was given to me years ago. I can't ...

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  20. Data Gravity

    In the last few days, I had an interesting exchange on Twitter about the concept of data gravity. For convenience, I'll include the relevant parts here.

    • Mat Ellis: Interesting piece by @mjasay link … @randybias is right on the money, data gravity is already a big deal on the cloud ...

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  21. Tiers Without Tears

    A lot of people have asked when GlusterFS is going to have support for tiering or Hierarchical Storage Management, particularly to stage data between SSDs and spinning disks. This is a pretty hot topic for these kinds of systems, and many - e.g. Ceph, HDFS, Swift - have announced upcoming support ...

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  22. The World Is Not Flat

    Way back when I was a young pup, either in college or after that but before I started my career, I got to use an operating system called MTS. That stands for Michigan Terminal System. It was created to run on IBM (and later Amdahl) mainframes, when U of M ...

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  23. Data Extortion

    This is a story about the dark side of moving your stuff into the cloud. It does have a (reasonably) happy ending, but along the way there are some important lessons to be learned about the relationship between cloud users and cloud providers, and how it's possible for people ...

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  24. Roll Back or Rock On?

    For a while now, Kyle Kingsbury has been doing some excellent work evaluating the consistency and other properties of various distributed databases. His latest target is Redis. Mostly I agree with the points he makes, and that Redis Cluster is subject to inexcusable data loss, but there is one point ...

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  25. Giving Thanks

    Thu 28 November 2013

    This was inspired both by a blog post elsewhere and by a nice email I got this morning thanking me for this blog (thanks Tristan). It seems like we all fail to give thanks, and nowhere more so than in the "gift economy" of open source. I'll start with ...

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  26. Shared Libraries are Obsolete

    I was around when shared libraries were still a new thing in the UNIX world. At the time, they seemed like a great idea. On multi-user systems like those I worked on at Encore, static linking meant not only having a separate copy of the same code in every program ...

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  27. Fixing Fsync

    When I wrote about how local filesystems suck a while ago, it sparked a bit of debate. Mostly it was just local-filesystem developers being defensive, but Dave Chinner did make the quite reasonable suggestion that I could help by proposing a better alternative to the fsync problem. I've owed ...

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  28. The "IOPS Myth" Myth

    It's nice to see more people becoming aware that IOPS are not the be-all and end-all of storage performance. Unfortunately, as with all consciousness raising, the newest converts are often the ones that take things too far. Thus, we get extreme claims like IOPS Are A Scam or Storage ...

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  29. Secure Email

    Ever since one of the talks at LISA, I've been thinking about secure email. My thoughts are nowhere near complete, but I need to get them out of my head and I do that by writing about them. Apologies in advance.

    I've actually been thinking for many years ...

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  30. Moot Comments

    I have a couple of posts coming up where I'll be soliciting feedback, so it's time to implement blog comments again. After looking at the alternatives, I eventually decided that Moot had the best combination of features for me (as the guy who has to integrate them) and ...

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  31. Comedic Open Storage

    Thu 24 October 2013

    tags: storage

    I've written before about some people's mania for object storage as an alternative to blocks and files. It's a valid model, but I do think its benefits are being pretty drastically oversold. Often there's a lot of FUD about distributed filesystems in particular, from people who ...

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  32. Leaning Out

    Thu 10 October 2013

    tags: working

    In April of '89 I left my family and friends to move from Michigan to Massachusetts for a programming job. The new job paid twice as much as my first programming job had, which means three times as much as I was making since that company laid me off, so ...

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  33. Model Checking

    Fri 27 September 2013

    tags: process

    Model checking is one of the most effective tools available for reducing the prevalence of bugs in highly concurrent code. Nonetheless, a surprising number of even very smart and very senior software developers and architects seem to know about it. Of the many such people I've worked with over ...

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  34. SAN Stalwarts and Wistful Thinking

    I've often said that open-source distributed storage solutions such as GlusterFS and Ceph are on the same side in a war against more centralized proprietary solutions, and that we have to finish that war before we start fighting over the spoils. Most recently I said that on Hacker News ...

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  35. Local Filesystems Suck

    Distributed filesystems represent an important use case for local filesystems. Local-filesystem developers can't seem to deal with that. That, in a nutshell, is one of the most annoying things about working on distributed filesystems. Sure, there are lots of fundamental algorithmic problems. Sure, networking stuff can be difficult too ...

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  36. Technical Credit

    To a first approximation, "software engineering" refers to all of the things you need to know when you take "programming" and try to scale it up - more code, more people, more time. You don't need an a civil engineer to dig a latrine, but you'd better have one ...

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  37. GlusterFS 3.5 Features

    It's time to let some cats out of some bags. As my loyal readers (yeah right) have surely noticed, things have been quiet around here. Part of that has been the result of vacations and such, but also there's a lot of stuff I just haven't felt ...

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  38. Avoiding Jet Lag

    Thu 25 July 2013

    tags: travel

    And now for something completely different...

    As part of my job - educating and evangelizing and whatever else you call it - I travel a fair amount. I know there are other people who travel ten times as much as I do, but then there are many more who travel less than ...

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  39. Startups and Patents

    Fri 19 July 2013

    tags: legal

    This should be a pretty familiar story to anyone in high tech by now. Startup makes something cool, becomes a target for patent litigation from what we used to call an NPE (Non Practicing Entity). Apparently the new term is PAE (Patent Assertion Entity) but I prefer an even more ...

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  40. Small Synchronous Writes

    Sometimes people ask me why I always use small synchronous writes for my performance comparisons. Surely (they say), there are other kinds of operations that are more common or more important. Yes there are (I say), and don't call me Shirley. But seriously, folks, there are definitely other kinds ...

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  41. Performance Measurement Pitfalls

    One of the problems with measuring and comparing performance of scalable systems is that any workload capable of producing meaningful results is going to be highly multi-threaded, and most developers don't know much about how to collect or interpret the results. After all, they hardly ever get any training ...

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  42. Two Weeks is Not a Sprint

    We're moving to an "agile" development process at work. Yes, we're becoming scrumbags. ;) One of the terms that really bothers me is "sprint" because I think of a sprint as a flat-out effort. That means minimal eating, sleeping, or time with family. Even hard-core hackers rarely do that ...

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  43. Lies, Damn Lies, and Parallels

    This apparently happened a while ago, but it recently came to my attention via LWN that James Bottomley has made the claim that "Gluster sucks" (not a paraphrase, those seem to be his exact words). Well, I couldn't just let that go by, could I? Why would he say ...

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  44. Package Managers

    There are many things that differentiate a true software engineer from a mere programmer. Most of them are unpleasant - planning releases, reviewing designs or code, testing, release engineering, and so on. One of the most odious tasks is packaging software. I'll admit that it's an area where my ...

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  45. Metadata Servers

    I was sad that I had to miss RICON East, because I knew they had a lot of great speakers lined up. I really liked James Hughes's presentation, but must take issue with slide 15.

    Metadata Servers

    Required by traditional filesystems (POSIX) to translate names to sectors

    Hard to ...

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  46. Starting Over

    You might have noticed that things look a bit different around here. OK, if you're reading this in an RSS reader then maybe not, but otherwise it's kind of obvious. I've switched platforms yet again, because I was feeling a bit blocked. Publishing new stuff using my ...

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