Mailing-List: contact hbase-user-help@hadoop.apache.org; run by ezmlm
Precedence: bulk
Reply-To: hbase-user@hadoop.apache.org
Received-SPF: pass (athena.apache.org: domain of ryanobjc@gmail.com designates
 209.85.223.186 as permitted sender)
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=mime-version:in-reply-to:references:date:message-id:subject:from:to
         :content-type:content-transfer-encoding;
        b=q5LlfhCKE2apAxS5mULcChidVm92CaW4vo/yHscVUb6l621SptxgCpvhDPaVy6gIGD
         6vVwRmfVuEbY3c5vGSjgp6wXxXBFgiERE4OpFTx5gVsMKQ74ZIkbmn6xKGDWH2pPE00N
         rDyyGMuKVy7qGIlxMZzcGCFnsOrUwuM/dHcxk=
MIME-Version: 1.0
In-Reply-To: <ca73442f1003011936g3c9bea6ay182a635dc374e349@mail.gmail.com>
References: <ca73442f1003011236x461bbbf6g9e61e7112ad84a90@mail.gmail.com>
	 <78568af11003011416k7528f6f9o44cf319dee367694@mail.gmail.com>
	 <74f4d40b1003011433i255459a8wc03de3ae0e76ec95@mail.gmail.com>
	 <ca73442f1003011936g3c9bea6ay182a635dc374e349@mail.gmail.com>
Date: Mon, 1 Mar 2010 22:57:23 -0800
Message-ID: <78568af11003012257k2c6d627ay6a26f671fef6a915@mail.gmail.com>
Subject: Re: Questions about HBase
From: Ryan Rawson <ryanobjc@gmail.com>
To: hbase-user@hadoop.apache.org
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

The ROOT/META are hosted on a regionserver so the system is
self-referential and self-hosting, furthermore it reduces the
dependency on the master to just a single duty of reassigning regions
as necessary.

-ryan

On Mon, Mar 1, 2010 at 7:36 PM, William Kang <weliam.cloud@gmail.com> wrote=
:
> And another question, why the ROOT table and META tables are not in the
> HBaseMaster's memory? Would this greatly degrade the performance?
> Thanks.
>
>
> William
>
>
> On Mon, Mar 1, 2010 at 5:33 PM, Erik Holstad <erikholstad@gmail.com> wrot=
e:
>
>> On Mon, Mar 1, 2010 at 2:16 PM, Ryan Rawson <ryanobjc@gmail.com> wrote:
>>
>> > Hi,
>> >
>> > 1. =A0We use in-memory indexes to get fast random reads. =A0Our index
>> > tells us to read block X of a file only retrieving a small amount of
>> > the file to satisfy the user's read.
>> >
>> > 2. =A0The row locking is not global - for each row there can only be 1
>> > thread doing a put at a time. =A0This serializes all puts to a single
>> > row. It is NOT global.
>> >
>>
>> So, this is me not understanding the difference between global locking a=
nd
>> waiting in a line until the tasks ahead of you are done :)
>>
>> >
>> > On Mon, Mar 1, 2010 at 12:36 PM, William Kang <weliam.cloud@gmail.com>
>> > wrote:
>> > > Hi guys,
>> > > I am new to HBase and have several questions. Would anybody kindly
>> answer
>> > > some of them?
>> > >
>> > > 1. Why HBase could provide a low-latency random access to files
>> compared
>> > to
>> > > HDFS?
>> > >
>> > > 2. By default, Only a single row at a time may be locked. Is it a
>> single
>> > > client who can only lock one or is it globally can only lock one? =
=A0If
>> > this
>> > > is the case, by default, will the performance be really bad?
>> > >
>> > > Many thanks!
>> > >
>> > >
>> > > William
>> > >
>> >
>>
>>
>>
>> --
>> Regards Erik
>>
>