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From Ken Hancock <>
Subject Re: Flush writer all time blocked
Date Thu, 29 Aug 2013 18:21:04 GMT
On Thu, Aug 29, 2013 at 1:57 PM, Robert Coli <> wrote:
> On Thu, Aug 29, 2013 at 10:49 AM, S C <> wrote:
>> I see a high count "All time blocked" for Flush Writer on nodetool tpstats.
>> Is it how many blocked ever since the server was online? Can somebody explain me
what it is? I really appreciate it.
> Yes.
> Flush Writer thread pool is the thread pool responsible for the part of memtable flush
that actually writes to disk.
> If you see it with a non-zero blocked number, you have at some time written to memory
significantly faster than you
> could flush to disk.

I don't think this is strictly true?  There's also the periodic flush
that can cause a storm of flushes if you have multiple column
families.  I sent out a query to the list last week on this topic but
didn't get any responses -- I'm very interested in this topic as I've
had to set my queue size fairly large to avoid this issue.


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