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From: Vijay <vijay2win@gmail.com>
Date: Tue, 8 Dec 2009 11:24:30 -0800
Message-ID: <9b40bc2a0912081124s12eeabf0m71df2656771cd676@mail.gmail.com>
Subject: Re: Configuring Cassandra
To: cassandra-user@incubator.apache.org
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a) Multiple DCs: Can I control that each key should store in each and every
data center? If it is possible, an example configuration will be helpful.
    you cannot.... and if you did the ring will break... consider Cassandra
in multiple DC as one big Ring..... We use Cassandra to have copies of all
data in all the DC's

Regards,
</VJ>




On Tue, Dec 8, 2009 at 5:56 AM, Mark Robson <markxr@gmail.com> wrote:

> I'm not an expert in Cassandra yet but I do know a little, here are some
> (attempted) answers:
>
> 2009/12/8 Rakesh Sharma <rakrma@gmail.com>
>
> b) Apart from nodeprobe and Jconsole is there any other node management
>> tool?
>>
>
> You can use any JMX application, apparently, to monitor it. This could be
> done e.g. via a command line script (assuming there is a convenient JMX CLI)
> and then hooked into your monitoring. I'd look there first. I have not tried
> this (yet).
>
> d) Can I control where a node will be added in the ring? How is it decided?
>> Primarily, I want to understand how the hot-spots can be handled?
>>
>
> You can pick the token manually before first startup; it gets read from the
> config file.
>
> Detecting hot-spots is not easy. If you use the OrderedPartitioner, then
> hot spots tend to occur where you put all your keys. The fix is to spread
> out your keys, or bunch up your nodes, but if you use time-based keys or
> similar, your key distribution will change over time so you can't win that
> way.
>
> Nodes can be decommissioned now (as of 0.5 I think) with the nodeprobe
> decommission command. You can then stop the node, clear all its data and
> re-bootstrap it with a different token. This is not an automatic or
> particularly fast or convenient process.
>
>
>> e) How a node data backup should be taken such that reads and writes at
>> that time are not effected (read or write locks)? Any tool/utility that can
>> be used?
>>
>
> The nodeprobe snapshot can take a snapshot of an individual node. You can
> of course schedule these to happen at (about) the same time.
>
>>
>> f) Can I take backups from each node and merge them on a single node? Or
>> it's not at all required?
>>
>
> Dunno, sounds nontrivial.
>
> Mark
>

--001636e1fb261a02ae047a3c87c2
Content-Type: text/html; charset=UTF-8
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a) Multiple DCs: Can I control that each key should store in each and
every data center? If it is possible, an example configuration will be
helpful.<br><span style=3D"color: rgb(255, 102, 0);">=C2=A0=C2=A0=C2=A0 you=
 cannot.... and if you did the ring will break... consider Cassandra in mul=
tiple DC as one big Ring..... We use Cassandra to have copies of all data i=
n all the DC&#39;s</span><br>

<br clear=3D"all">Regards,<br>&lt;/VJ&gt;<br><br><br>
<br><br><div class=3D"gmail_quote">On Tue, Dec 8, 2009 at 5:56 AM, Mark Rob=
son <span dir=3D"ltr">&lt;<a href=3D"mailto:markxr@gmail.com">markxr@gmail.=
com</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"bor=
der-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-=
left: 1ex;">

<div class=3D"gmail_quote">I&#39;m not an expert in Cassandra yet but I do =
know a little, here are some (attempted) answers:<br><br>2009/12/8 Rakesh S=
harma <span dir=3D"ltr">&lt;<a href=3D"mailto:rakrma@gmail.com" target=3D"_=
blank">rakrma@gmail.com</a>&gt;</span><div class=3D"im">

<br>
<blockquote class=3D"gmail_quote" style=3D"border-left: 1px solid rgb(204, =
204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">b) Apart from <sp=
an style=3D"font-family: arial,helvetica,sans-serif;"></span><span style=3D=
"font-family: arial,helvetica,sans-serif;">nodeprobe</span><span style=3D"f=
ont-family: arial,helvetica,sans-serif;"> and </span>Jconsole is there any =
other node management tool?<br>


</blockquote></div><div><br>You can use any JMX application, apparently, to=
 monitor it. This could be done e.g. via a command line script (assuming th=
ere is a convenient JMX CLI) and then hooked into your monitoring. I&#39;d =
look there first. I have not tried this (yet).<br>


<br></div><div class=3D"im"><blockquote class=3D"gmail_quote" style=3D"bord=
er-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-l=
eft: 1ex;">d) Can I control where a node will be added in the ring? How is =
it decided? Primarily, I want to understand how the hot-spots can be handle=
d?<br>


</blockquote></div><div><br>You can pick the token manually before first st=
artup; it gets read from the config file.<br><br>Detecting hot-spots is not=
 easy. If you use the OrderedPartitioner, then hot spots tend to occur wher=
e you put all your keys. The fix is to spread out your keys, or bunch up yo=
ur nodes, but if you use time-based keys or similar, your key distribution =
will change over time so you can&#39;t win that way.<br>


<br>Nodes can be decommissioned now (as of 0.5 I think) with the nodeprobe =
decommission command. You can then stop the node, clear all its data and re=
-bootstrap it with a different token. This is not an automatic or particula=
rly fast or convenient process.<br>


=C2=A0</div><div class=3D"im"><blockquote class=3D"gmail_quote" style=3D"bo=
rder-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding=
-left: 1ex;">e) How a node data backup should be taken such that reads and =
writes at that time are not effected (read or write locks)? Any tool/utilit=
y that can be used?<br>


</blockquote></div><div><br>The nodeprobe snapshot can take a snapshot of a=
n individual node. You can of course schedule these to happen at (about) th=
e same time.=C2=A0 <br></div><div class=3D"im"><blockquote class=3D"gmail_q=
uote" style=3D"border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0=
pt 0.8ex; padding-left: 1ex;">



<br>f) Can I take backups from each node and merge them on a single node? O=
r it&#39;s not at all required?<br></blockquote><div><br></div></div></div>=
Dunno, sounds nontrivial.<br><font color=3D"#888888"><br>Mark<br>
</font></blockquote></div><br>

--001636e1fb261a02ae047a3c87c2--