Mailing-List: contact user-help@cassandra.apache.org; run by ezmlm
Precedence: bulk
Reply-To: user@cassandra.apache.org
Received-SPF: pass (nike.apache.org: domain of springrider@gmail.com
 designates 209.85.215.180 as permitted sender)
MIME-Version: 1.0
In-Reply-To: 
 <CAOA66tFakdCG4deM-Jdo0S2e-tLUtE=_D1v_Qtc1R-4x=csTuw@mail.gmail.com>
References: 
 <CAOA66tF+-Ro5=VMiPp9BodJEva=AUuS=qcTshuqd+uy0JqCWRA@mail.gmail.com>
 <4B50E052B4E82B4AA6961853D610D3C433B62890ED@MBX75.ad2.softcom.biz>
 <CALdd-zii-N3k-jPvZ0jR5XOc601tvy=o1Et_RgGk=5ypf5nUtQ@mail.gmail.com>
 <CAOA66tFakdCG4deM-Jdo0S2e-tLUtE=_D1v_Qtc1R-4x=csTuw@mail.gmail.com>
From: Yan Chunlu <springrider@gmail.com>
Date: Mon, 25 Jul 2011 21:17:27 +0800
Message-ID: 
 <CAOA66tGgfX_kuVejfkOk8gawW_uw4snEt85F-tOa=Umi6+A1kQ@mail.gmail.com>
Subject: Re: do I need to add more nodes? minor compaction eat all IO
To: user@cassandra.apache.org
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

as the wiki suggested:
http://wiki.apache.org/cassandra/LargeDataSetConsiderations
Adding nodes is a slow process if each node is responsible for a large
amount of data. Plan for this; do not try to throw additional hardware
at a cluster at the last minute.


I really would like to know what's the status of my cluster, if it is norma=
l


On Mon, Jul 25, 2011 at 8:59 PM, Yan Chunlu <springrider@gmail.com> wrote:
> I am using normal SATA disk, =A0actually I was worrying about whether it
> is okay if every time cassandra using all the io resources?
> further more when is the good time to add more nodes when I was just
> using normal SATA disk and with 100r/s it could reach 100 %util....
>
> how large the data size it should be on each node?
>
>
> below is my iostat -x 2 when doing node repair, I have to repair
> column family separately otherwise the load will be more crazy:
>
> Device: =A0 =A0 =A0 =A0 rrqm/s =A0 wrqm/s =A0 =A0 r/s =A0 =A0 w/s =A0 =A0=
rMB/s =A0 =A0wMB/s
> avgrq-sz avgqu-sz =A0 await r_await w_await =A0svctm =A0%util
> sda =A0 =A0 =A0 =A0 =A0 =A0 =A0 1.50 =A0 =A0 1.50 =A0121.50 =A0 14.00 =A0=
 =A0 3.68 =A0 =A0 0.30
> 60.19 =A0 116.98 1569.46 =A0 59.49 14673.86 =A0 7.38 100.00
>
>
>
>
>
>
> On Sun, Jul 24, 2011 at 8:04 AM, Jonathan Ellis <jbellis@gmail.com> wrote=
:
>> On Sat, Jul 23, 2011 at 4:16 PM, Francois Richard <frichard@xobni.com> w=
rote:
>>> My understanding is that during compaction cassandra does a lot of non =
sequential readsa then dumps the results with a big sequential write.
>>
>> Compaction reads and writes are both sequential, and 0.8 allows
>> setting a MB/s to cap compaction at.
>>
>> As to the original question "do I need to add more machines" I'd say
>> that depends more on whether your application's SLA is met, than what
>> % io util spikes to.
>>
>> --
>> Jonathan Ellis
>> Project Chair, Apache Cassandra
>> co-founder of DataStax, the source for professional Cassandra support
>> http://www.datastax.com
>>
>