Mailing-List: contact user-help@cassandra.apache.org; run by ezmlm
Precedence: bulk
Reply-To: user@cassandra.apache.org
Received-SPF: pass (athena.apache.org: domain of jbellis@gmail.com designates
 209.85.161.172 as permitted sender)
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=mime-version:in-reply-to:references:from:date:message-id:subject:to
         :content-type:content-transfer-encoding;
        b=NZVq+Xam5jk3yBipbJYWwlbELXUJrfLq7btxRdld0BhUN5sBGCkezwPQFK5LqrkK4C
         EPV1Da1Ekks9ZpvNlhkwvRd1mmaLJoCUg4pN/ISrf+6AEtKJombqwYUNsrH26k5ijZLO
         C7JEWLKDmBz413wMQKDZ5MUT3a0+/9i9lcnNQ=
MIME-Version: 1.0
In-Reply-To: <AANLkTikoFQ7mL73XEN_uzGubJK7d2XzV4HVJcFwz2Rv+@mail.gmail.com>
References: <AANLkTim2SEbvA3kX_7DZ8XE23zUF1i=_rdEpTVsx0SeL@mail.gmail.com>
 <AANLkTinqdMJ22FkGpSZpFYMghDCAisGuP2RuOjj20JwV@mail.gmail.com>
 <AANLkTikoFQ7mL73XEN_uzGubJK7d2XzV4HVJcFwz2Rv+@mail.gmail.com>
From: Jonathan Ellis <jbellis@gmail.com>
Date: Fri, 3 Sep 2010 07:08:37 -0700
Message-ID: <AANLkTikbf-qacDXdV=mCeWzP-_K4tRLixAyE1DXfTkM7@mail.gmail.com>
Subject: Re: the process of reading and writing
To: user@cassandra.apache.org
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

To the degree that this suggests that there is a "master" node for
each range, IMO it is a "bug" in the paper.  (There are several of
these.)  Certainly there are no master nodes in Cassandra.

On Fri, Sep 3, 2010 at 12:02 AM, Ying Tang <ivytang0812@gmail.com> wrote:
> In dynamo's paper ,it says:
> Each key, k, is=A0assigned to a coordinator node .
> The coordinator is in charge of the replication of the data items=A0that =
fall
> within its range.
> On Fri, Sep 3, 2010 at 2:56 PM, Benjamin Black <b@b3k.us> wrote:
>>
>> On Thu, Sep 2, 2010 at 8:19 PM, Ying Tang <ivytang0812@gmail.com> wrote:
>> > Recently , i read the paper about Cassandra again .
>> > And now i have some concepts about =A0the reading and writing .
>> > We all know Cassandra uses NWR ,
>> > When read :
>> > the request ---> a random node in Cassandra .This node acts as a proxy
>> > ,and
>> > it routes the request.
>> > Here ,
>> > 1.=A0the proxy node route this request to this key's coordinator , the
>> > coordinator then routes request to other N-1 nodes =A0 OR =A0 the prox=
y
>> > routes
>> > the read request to N nodes ?
>>
>> The coordinator node is the proxy node.
>>
>> > 2. If it is the former situation , the read repair occurs on the=A0=A0=
key's
>> > coordinator ?
>> > =A0=A0 If =A0it is the latter , the=A0=A0read repair occurs on the pro=
xy node ?
>>
>> Depends on the CL requested. =A0QUORUM and ALL cause the RR to be
>> performed by the coordinator. =A0ANY and ONE cause RR to be delegated to
>> one of the replicas for the key.
>>
>> > When write :
>> > the request ---> a random node in Cassandra .This node acts as a proxy
>> > ,and
>> > it routes the request.
>> > Here ,
>> > 3.=A0the proxy node route this request to this key's coordinator , the
>> > coordinator then routes request to other N-1 nodes =A0 OR =A0 the prox=
y
>> > routes
>> > the request to N nodes ?
>> >
>>
>> For writes, the coordinator sends the writes directly to the replicas
>> regardless of CL (rather than delegating for weakly consistent CLs).
>>
>> > 4. The N isn't the data's copy numbers , it's just a =A0range . In thi=
s =A0N
>> > range , there must be W copies .So W is the copy numbers.
>> > So in this N range , R+W>N can=A0guarantee the data's=A0validity. Righ=
t?
>> >
>>
>> Sorry, I can't even parse this.
>>
>>
>> b
>
>
>
> --
> Best regards,
> Ivy Tang
>
>
>


--=20
Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of Riptano, the source for professional Cassandra support
http://riptano.com