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Date: Mon, 25 Mar 2013 11:37:04 -0600
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Subject: Re: cfhistograms
From: Derek Williams <derek@fyrie.net>
To: user@cassandra.apache.org
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On Mon, Mar 25, 2013 at 10:36 AM, Brian Tarbox <tarbox@cabotresearch.com>wrote:

> I think we all go through this learning curve.  Here is the answer I gave
> last time this question was asked:
>
> The output of this command seems to make no sense unless I think of it as
> 5 completely separate histograms that just happen to be displayed
> together.
>
> Using this example output should I read it as: my reads all took either 1
> or 2 sstable.  And separately, I had write latencies of 3,7,19.  And
> separately I had read latencies of 2, 8,69, etc?
>

Little correction: The actual value is in the Offset column, all the other
columns are the count for that bucket of the histogram. For example in
write latency the 3, 7, and 19 refer to how many requests had that latency.
3 write requests took 17us, 7 requests took 20us, and 19 took 24us.

-- 
Derek Williams

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<div dir=3D"ltr"><div class=3D"gmail_extra">On Mon, Mar 25, 2013 at 10:36 A=
M, Brian Tarbox <span dir=3D"ltr">&lt;<a href=3D"mailto:tarbox@cabotresearc=
h.com" target=3D"_blank">tarbox@cabotresearch.com</a>&gt;</span> wrote:<br>=
<div class=3D"gmail_quote">
<blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-=
left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;p=
adding-left:1ex"><div dir=3D"ltr">I think we all go through this learning c=
urve. =C2=A0Here is the answer I gave last time this question was asked:<di=
v>
<br></div><div><span style=3D"font-family:arial,sans-serif;font-size:13px">=
The output of this command seems to make no sense unless I think of it as 5=
 completely separate=C2=A0</span><span style=3D"font-family:arial,sans-seri=
f;font-size:13px">histograms</span><span style=3D"font-family:arial,sans-se=
rif;font-size:13px">=C2=A0that just happen to be displayed together.</span>=
<div style=3D"font-family:arial,sans-serif;font-size:13px">

<br></div><div style=3D"font-family:arial,sans-serif;font-size:13px">Using =
this example output should I read it as: my reads all took either 1 or 2 ss=
table. =C2=A0And separately, I had write latencies of 3,7,19. =C2=A0And sep=
arately I had read latencies of 2, 8,69, etc?</div>
</div></div></blockquote><div><br></div><div style>Little correction: The a=
ctual value is in the Offset column, all the other columns are the count fo=
r that bucket of the histogram. For example in write latency the 3, 7, and =
19 refer to how many requests had that latency. 3 write requests took 17us,=
 7 requests took 20us, and 19 took 24us.=C2=A0</div>
</div><div><br></div>-- <br>Derek Williams
</div></div>

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