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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: Read Performance
Date Wed, 31 Mar 2010 03:59:22 GMT
What is your row cache hit rate?

By "still slow" do you mean "no change observed" or "faster but not
fast enough?"

On Tue, Mar 30, 2010 at 10:47 PM, James Golick <jamesgolick@gmail.com> wrote:
> We are starting to use cassandra to power our activity feed. The way we
> organize our data is simple. "Event"s live in a CF called Events and are
> keyed by a UUID. The timelines themselves live in a CF called Timelines,
> which is keyed by user id (i.e. "1229") and contains a event uuids as column
> names (sorted by TimeUUIDType).
> To load a feed, we get a slice of the timeline CF for that user, then
> multiget all of the corresponding events.
> Loading the slice of the timeline is reasonably fast at 4-6ms. But,
> multigetting the events is terribly slow - on the order of 35-100ms.
> To alleviate the problem, we write events through to memcached and use a
> memcached multiget in front of the cassandra multiget. We have enough cache
> space to get upwards of a 99% hit rate, which makes loading the events
> extremely fast, but it would be nice to make use of the 24GB of memory in
> our cassandra nodes.
> We're on 0.6, and I've enabled the row cache. It seems to have data in it,
> but it's still slow.
> So, am I doing something wrong, or is this the expected perf?
> - James

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