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Date: Thu, 1 Aug 2013 13:16:15 -0700
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Subject: Re: How often to run `nodetool repair`
From: Andrey Ilinykh <ailinykh@gmail.com>
To: user@cassandra.apache.org
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On Thu, Aug 1, 2013 at 12:26 PM, Robert Coli <rcoli@eventbrite.com> wrote:

> On Thu, Aug 1, 2013 at 9:35 AM, Carl Lerche <me@carllerche.com> wrote:
>
>> I read in the docs that `nodetool repair` should be regularly run unless
>> no delete is ever performed. In my app, I never delete, but I heavily use
>> the ttl feature. Should repair still be run regularly? Also, does repair
>> take less time if it is run regularly? If not, is there a way to
>> incrementally run it? It seems that when I do run repair, it takes a long
>> time and causes high amounts CPU usage and iowait.
>>
>
> TTL is effectively DELETE; you need to run a repair once every
> gc_grace_seconds. If you don't, data might un-delete itself.
>

How is it possible? Every replica has TTL, so it when it expires every
replica has tombstone. I don't see how you can get data with no tombstone.
What do I miss?

Andrey

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<div dir=3D"ltr"><br><div class=3D"gmail_extra"><br><br><div class=3D"gmail=
_quote">On Thu, Aug 1, 2013 at 12:26 PM, Robert Coli <span dir=3D"ltr">&lt;=
<a href=3D"mailto:rcoli@eventbrite.com" target=3D"_blank">rcoli@eventbrite.=
com</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div dir=3D"ltr"><div class=3D"im">On Thu, A=
ug 1, 2013 at 9:35 AM, Carl Lerche <span dir=3D"ltr">&lt;<a href=3D"mailto:=
me@carllerche.com" target=3D"_blank">me@carllerche.com</a>&gt;</span> wrote=
:<br>
</div><div class=3D"gmail_extra"><div class=3D"gmail_quote"><div class=3D"i=
m">

<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"><div>I read in the docs that `nodetool re=
pair` should be regularly run unless no delete is ever performed. In my app=
, I never delete, but I heavily use the ttl feature. Should repair still be=
 run regularly? Also, does repair take less time if it is run regularly? If=
 not, is there a way to incrementally run it? It seems that when I do run r=
epair, it takes a long time and causes high amounts CPU usage and iowait.</=
div>

</div></blockquote><div><br></div></div><div>TTL is effectively DELETE; you=
 need to run a repair once every gc_grace_seconds. If you don&#39;t, data m=
ight un-delete itself.=A0</div></div></div></div></blockquote><div><br></di=
v>
<div>How is it possible? Every replica has TTL, so it when it expires every=
 replica has tombstone. I don&#39;t see how you can get data with no tombst=
one. What do I miss?</div><div><br></div><div>Andrey=A0</div></div><br></di=
v>
</div>

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