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 ...
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 ...
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 ...
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 ...
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 ...
I've written and talked many times about storage benchmarking. Mostly, I've focused on how to run tests and analyze results. This time, I'd like to focus on the parts that come before that - how you set up the system so that you have at least some chance ...
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 ...
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 ...
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.
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 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 ...
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 ...
(This started as a Hacker News discussion about an article on
Advogato. The articles title/premise is "Why You Need STONITH" where
"STONITH" means "Shoot The Other Node In The Head" and is an important concept
in old-school HA. I might even have been present when the acronym was coined ...
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 ...
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 ...
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 ...
A while ago, I got an Ergotron WorkFit-S sit/stand monitor mount. I love
it, and have talked about it to plenty of people. Yesterday I joined a Hacker
News discussion about standing desks, and it left me with some thoughts
that I'd rather share here than there, so ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...