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From: sankalp kohli <kohlisankalp@gmail.com>
Date: Fri, 6 Sep 2013 10:26:31 -0700
Message-ID: 
 <CAEPxca2N--pNoLQ2VVt2LdzeUuryth-TPNj3EswBJTK8naAvWA@mail.gmail.com>
Subject: Re: Cassandra 1.2.4 - Unflushed data lost on restart
To: user@cassandra.apache.org
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You should be using replication. Not all machines will power off at the
same time.
Regarding changing the fsync setting, even if you choose it to be fully
sync, there have been many studies which have shown that data was lost on
many SSDs even after fsync has returned.
So I will fix this problem by replication and not changing the fsync stuff.


On Fri, Sep 6, 2013 at 10:21 AM, Mohit Anchlia <mohitanchlia@gmail.com>wrote:

> Are you not using RF >= 3 ?
>
>
> On Fri, Sep 6, 2013 at 10:14 AM, Thapar, Vishal (HP Networking) <
> vthapar@hp.com> wrote:
>
>> My usage requirements are such that there should be least possible data
>> loss even in case of a poweroff. When you say clean shutdown do you mean
>> Cassandra service stop?
>>
>> I ran across this issue when testing out different scenarios to figure
>> out what would be best configuration for my requirements, will consider
>> batch mode as 10 seconds window might be too much for some of my use cases.
>>
>> Thanks for the reply,
>> Vishal.
>> -----------------------------------------------
>> From: Robert Coli [mailto:rcoli@eventbrite.com]
>> Sent: Friday, September 06, 2013 10:35 PM
>> To: user@cassandra.apache.org
>> Subject: Re: Cassandra 1.2.4 - Unflushed data lost on restart
>>
>> On Fri, Sep 6, 2013 at 2:42 AM, Thapar, Vishal (HP Networking) <
>> vthapar@hp.com> wrote:
>> I am running Cassandra 1.2.4 in standalone mode and see a data loss when
>> I stop/start Cassandra [kill the task].
>>
>> Clean shutdown waits for commitlog flush. Unclean shutdown does not. In
>> default periodic mode, this could mean up to 10 seconds of loss. If you
>> don't want to lose up to 10 seconds, use batch commitlog mode or... just
>> shut down cleanly?
>>
>> There are also cases in your vintage Cassandra where data in secondary
>> indexes has not been available, in case you are querying on those.
>>
>> =Rob
>>
>
>

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<div dir=3D"ltr">You should be using replication. Not all machines will pow=
er off at the same time.=A0<div style>Regarding changing the fsync setting,=
 even if you choose it to be fully sync, there have been many studies which=
 have shown that data was lost on many SSDs even after fsync has returned.=
=A0</div>

<div style>So I will fix this problem by replication and not changing the f=
sync stuff.=A0</div></div><div class=3D"gmail_extra"><br><br><div class=3D"=
gmail_quote">On Fri, Sep 6, 2013 at 10:21 AM, Mohit Anchlia <span dir=3D"lt=
r">&lt;<a href=3D"mailto:mohitanchlia@gmail.com" target=3D"_blank">mohitanc=
hlia@gmail.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">Are you not using RF &gt;=3D 3 ?<div class=
=3D"HOEnZb"><div class=3D"h5"><br><br><div class=3D"gmail_quote">On Fri, Se=
p 6, 2013 at 10:14 AM, Thapar, Vishal (HP Networking) <span dir=3D"ltr">&lt=
;<a href=3D"mailto:vthapar@hp.com" target=3D"_blank">vthapar@hp.com</a>&gt;=
</span> wrote:<br>


<blockquote style=3D"margin:0px 0px 0px 0.8ex;padding-left:1ex;border-left-=
color:rgb(204,204,204);border-left-width:1px;border-left-style:solid" class=
=3D"gmail_quote">My usage requirements are such that there should be least =
possible data loss even in case of a poweroff. When you say clean shutdown =
do you mean Cassandra service stop?<br>


<br>
I ran across this issue when testing out different scenarios to figure out =
what would be best configuration for my requirements, will consider batch m=
ode as 10 seconds window might be too much for some of my use cases.<br>


<br>
Thanks for the reply,<br>
Vishal.<br>
-----------------------------------------------<br>
From: Robert Coli [mailto:<a href=3D"mailto:rcoli@eventbrite.com" target=3D=
"_blank">rcoli@eventbrite.com</a>]<br>
Sent: Friday, September 06, 2013 10:35 PM<br>
To: <a href=3D"mailto:user@cassandra.apache.org" target=3D"_blank">user@cas=
sandra.apache.org</a><br>
Subject: Re: Cassandra 1.2.4 - Unflushed data lost on restart<br>
<div><div><br>
On Fri, Sep 6, 2013 at 2:42 AM, Thapar, Vishal (HP Networking) &lt;<a href=
=3D"mailto:vthapar@hp.com" target=3D"_blank">vthapar@hp.com</a>&gt; wrote:<=
br>
I am running Cassandra 1.2.4 in standalone mode and see a data loss when I =
stop/start Cassandra [kill the task].<br>
<br>
Clean shutdown waits for commitlog flush. Unclean shutdown does not. In def=
ault periodic mode, this could mean up to 10 seconds of loss. If you don=
9;t want to lose up to 10 seconds, use batch commitlog mode or... just shut=
 down cleanly?<br>


<br>
There are also cases in your vintage Cassandra where data in secondary inde=
xes has not been available, in case you are querying on those.<br>
<br>
=3DRob=A0<br>
</div></div></blockquote></div><br>
</div></div></blockquote></div><br></div>

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