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Date: Fri, 20 Jun 2014 15:51:53 -0700
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Subject: Re: Using Cassandra as cache
From: Robert Coli <rcoli@eventbrite.com>
To: "user@cassandra.apache.org" <user@cassandra.apache.org>
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On Fri, Jun 20, 2014 at 3:09 PM, DuyHai Doan <doanduyhai@gmail.com> wrote:
> @Robert: do we still need to cleanup manually snapshot when truncating ?
I remembered that on the 1.2 branch, even though the auto_snapshot param
was set to false, truncating leads to snapshot creation that forced us to
manually remove the snapshot folder on disk

Both DROP and TRUNCATE auto_snapshot by default, yes.

> Can you please explain what problems DROP/CREATE keyspace may cause?

Check JIRA, but in general currently DROP/CREATE same entity can cause
bugs. DROP/CREATE with always unique names should be fine.

> Seems like truncate working per column family and I have up to 10.

So TRUNCATE all 10?

> Can working RF=2 and CL=ANY result in any problem with consistency? I am
not sure I can have problems with consistency if I don't do updates, only
writes and reads. Can I?

CL=ANY is a problem with consistency. Wherever you read the instruction to
consider ever using it for any reason, strongly consider never visiting
that site again.

RF=2 means you can't use QUORUM without using CL.ALL. Not being able to use
QUORUM can result in consistency problems. Using CL.ALL results in
availability problems.

=Rob

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<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote">On F=
ri, Jun 20, 2014 at 3:09 PM, DuyHai Doan <span dir=3D"ltr">&lt;<a href=3D"m=
ailto:doanduyhai@gmail.com" target=3D"_blank">doanduyhai@gmail.com</a>&gt;<=
/span> wrote:</div>
<div class=3D"gmail_quote">&gt; @Robert: do we still need to cleanup manual=
ly snapshot when truncating ? I remembered that on the 1.2 branch, even tho=
ugh the auto_snapshot param was set to false, truncating leads to snapshot =
creation that forced us to manually remove the snapshot folder on disk<div>
<br></div><div>Both DROP and TRUNCATE auto_snapshot by default, yes.</div><=
div><br></div><div>&gt;=C2=A0<span style=3D"font-family:arial,sans-serif;fo=
nt-size:13px">Can you please explain what problems DROP/CREATE keyspace may=
 cause?</span></div>
<div><span style=3D"font-family:arial,sans-serif;font-size:13px"><br></span=
></div><div><span style=3D"font-family:arial,sans-serif;font-size:13px">Che=
ck JIRA, but in general currently DROP/CREATE same entity can cause bugs. D=
ROP/CREATE with always unique names should be fine.</span></div>
<div><br></div><div>&gt;=C2=A0<span style=3D"font-family:arial,sans-serif;f=
ont-size:13px">Seems like truncate working per column family and I have up =
to 10.</span></div><div><span style=3D"font-family:arial,sans-serif;font-si=
ze:13px"><br>
</span></div><div><span style=3D"font-family:arial,sans-serif;font-size:13p=
x">So TRUNCATE all 10?</span></div><div><span style=3D"font-family:arial,sa=
ns-serif;font-size:13px"><br></span></div><div><span style=3D"font-family:a=
rial,sans-serif;font-size:13px">&gt;=C2=A0</span><span style=3D"font-family=
:arial,sans-serif;font-size:13px">Can working RF=3D2 and CL=3DANY result in=
 any problem with consistency? I am not sure I can have problems with consi=
stency if I don&#39;t do updates, only writes and reads. Can I?</span></div=
>
<div><span style=3D"font-family:arial,sans-serif;font-size:13px"><br></span=
></div><div><span style=3D"font-family:arial,sans-serif;font-size:13px">CL=
=3DANY is a problem with consistency. Wherever you read the instruction to =
consider ever using it for any reason, strongly consider never visiting tha=
t site again.</span></div>
<div><span style=3D"font-family:arial,sans-serif;font-size:13px"><br></span=
></div><div><span style=3D"font-family:arial,sans-serif;font-size:13px">RF=
=3D2 means you can&#39;t use QUORUM without using CL.ALL. Not being able to=
 use QUORUM can result in consistency problems. Using CL.ALL results in ava=
ilability problems.</span></div>
<div><br></div><div>=3DRob</div><div>=C2=A0</div></div></div></div>

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