graphite-dev team mailing list archive

[Elliot Murphy <elliot@xxxxxxxxxxxxx>]

Hi Chris, Kraig,

It's really cool to read about this work with Cassandra. At Canonical,
we are looking to consolidate and replace multiple graphing systems
that have sprung up over time. We have been running cricket for about
the last 6 years, and would like to replace it with something more
modern - one of the big problems we have with cricket right now is
that it loses data once you pass the time period defined in your RRD
database. So we've also got a system storing some graphing data in
postgres. I've been pretty impressed with graphite and how shiny it
is, but haven't used it in anger yet.

This might be a dumb question, but would using this Cassandra backend
with Graphite potentially address the problem of not wanting to ever
lose old data points? Or does the whisper design already get rid of
that limitation?

On Thu, Mar 18, 2010 at 2:01 AM, Chris Davis <chrismd@xxxxxxxxx> wrote:
> Wow, thanks for the performance numbers Kraig. Yes I am definitely
> interested in learning more about Cassandra. I have not had a chance to try
> it out yet myself but it sounds pretty cool and it is nice to see someone
> has it running in a working system. I have also been hearing a lot of buzz
> about Redis lately (http://code.google.com/p/redis/) and some users are
> looking into using that as a carbon-cache replacement as well. Again I
> haven't had a chance to mess around with it myself so I don't know all that
> much about it. I am cc'ing the mailing list so we can open this up to a
> broader discussion, possibly about Redis as well.
> I am very curious about how Cassandra actually works and I am also curious
> about the %iowait numbers from your testing. In particular the %iowait times
> are nearly zero on the Cassandra servers. Presumably Cassandra is getting
> everything persisted to disk with consistent performance over time? If it is
> then I think it would be a good idea to test a scenario where there is both
> a lot of metrics being written as well as a lot of metrics being
> retrieved. The reason this is important is because there are two I/O access
> patterns heavily used by Graphite that are in complete conflict with one
> another.


-- 
Elliot Murphy | https://launchpad.net/~statik/