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Posted to user@hbase.apache.org by Naama Kraus <na...@gmail.com> on 2008/06/15 12:38:46 UTC
HBase and locality issues
Hi,
I have some questions regarding HBase and locality issues - I'd appreciate
some explanations and clarifications.
I understand HBase is built on top of HDFS.
Say an HRegionServer creates a HStoreFile where it puts some column family
content. Does HDFS split the file to multiple HDFS blocks and distributes
them around bunch of machines ? If that's the case, when the region server
needs to actually access the files, does HDFS underneath communicates remote
machines to read the various blocks ? Doesn't it hurt performance since
there is no locality in data access (region server actually works on remote
blocks).
Or is the HStoreFile implemented in some other way which writes it to the
local disks of the region server node machine that owns it ? If so, then how
? Does this code overrides the HDFS behavior ?
Another related question is about Map Reduce and HBase. When a MapReduce
job runs on top of HBase - i.e. gets a table as an input. How does the
MapReduce framework know how to schedule map tasks near data ? Does it
have any knowledge of the actual location of the data pieces composing the
table to be processed ?
I'd be also glad to get pointers to the related source code (classes).
Thanks for any information,
Naama
--
oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo
00 oo 00 oo
"If you want your children to be intelligent, read them fairy tales. If you
want them to be more intelligent, read them more fairy tales." (Albert
Einstein)
Re: HBase and locality issues
Posted by Naama Kraus <na...@gmail.com>.
Thanks for the helpful information.
Naama
On Mon, Jun 16, 2008 at 12:17 AM, Jim Kellerman <ji...@powerset.com> wrote:
> Comments inline below.
>
> ---
> Jim Kellerman, Senior Engineer; Powerset
>
>
> > -----Original Message-----
> > From: Naama Kraus [mailto:naamakraus@gmail.com]
> > Sent: Sunday, June 15, 2008 3:39 AM
> > To: hbase-user@hadoop.apache.org
> > Subject: HBase and locality issues
> >
> > Hi,
> >
> > I have some questions regarding HBase and locality issues -
> > I'd appreciate some explanations and clarifications.
> >
> > I understand HBase is built on top of HDFS.
> > Say an HRegionServer creates a HStoreFile where it puts some
> > column family content. Does HDFS split the file to multiple
> > HDFS blocks and distributes them around bunch of machines ?
>
> Yes. HStoreFile is currently implemented using org.apache.hadoop.io.MapFile
>
> > If that's the case, when the region server needs to actually
> > access the files, does HDFS underneath communicates remote
> > machines to read the various blocks ?
>
> Sometimes. If a requested block is local, HDFS will try to get that one.
>
> > Doesn't it hurt performance since there is no locality in data access
> > (region server actually works on remote blocks).
>
> Somewhat. We have other areas that we have identified as larger performance
> bottlenecks that need to be addressed first.
>
> > Or is the HStoreFile implemented in some other way which
> > writes it to the local disks of the region server node
> > machine that owns it ?
>
> No. Blocks are placed according to HDFS strategies.
>
> > If so, then how ? Does this code overrides the HDFS behavior ?
>
> It doesn't.
>
> > Another related question is about Map Reduce and HBase. When
> > a MapReduce job runs on top of HBase - i.e. gets a table as
> > an input. How does the MapReduce framework know how to
> > schedule map tasks near data ? Does it have any knowledge of
> > the actual location of the data pieces composing the table to
> > be processed ?
>
> No. It is on our list of things to do. See HBASE-57
>
> > I'd be also glad to get pointers to the related source code (classes).
> >
> > Thanks for any information,
> > Naama
> >
> > --
> > oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00
> > oo 00 oo 00 oo 00 oo 00 oo "If you want your children to be
> > intelligent, read them fairy tales. If you want them to be
> > more intelligent, read them more fairy tales." (Albert
> > Einstein)
>
> No virus found in this outgoing message.
> Checked by AVG.
> Version: 8.0.100 / Virus Database: 270.3.0/1503 - Release Date: 6/14/2008
> 6:02 PM
>
--
oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo
00 oo 00 oo
"If you want your children to be intelligent, read them fairy tales. If you
want them to be more intelligent, read them more fairy tales." (Albert
Einstein)
RE: HBase and locality issues
Posted by Jim Kellerman <ji...@powerset.com>.
Comments inline below.
---
Jim Kellerman, Senior Engineer; Powerset
> -----Original Message-----
> From: Naama Kraus [mailto:naamakraus@gmail.com]
> Sent: Sunday, June 15, 2008 3:39 AM
> To: hbase-user@hadoop.apache.org
> Subject: HBase and locality issues
>
> Hi,
>
> I have some questions regarding HBase and locality issues -
> I'd appreciate some explanations and clarifications.
>
> I understand HBase is built on top of HDFS.
> Say an HRegionServer creates a HStoreFile where it puts some
> column family content. Does HDFS split the file to multiple
> HDFS blocks and distributes them around bunch of machines ?
Yes. HStoreFile is currently implemented using org.apache.hadoop.io.MapFile
> If that's the case, when the region server needs to actually
> access the files, does HDFS underneath communicates remote
> machines to read the various blocks ?
Sometimes. If a requested block is local, HDFS will try to get that one.
> Doesn't it hurt performance since there is no locality in data access
> (region server actually works on remote blocks).
Somewhat. We have other areas that we have identified as larger performance
bottlenecks that need to be addressed first.
> Or is the HStoreFile implemented in some other way which
> writes it to the local disks of the region server node
> machine that owns it ?
No. Blocks are placed according to HDFS strategies.
> If so, then how ? Does this code overrides the HDFS behavior ?
It doesn't.
> Another related question is about Map Reduce and HBase. When
> a MapReduce job runs on top of HBase - i.e. gets a table as
> an input. How does the MapReduce framework know how to
> schedule map tasks near data ? Does it have any knowledge of
> the actual location of the data pieces composing the table to
> be processed ?
No. It is on our list of things to do. See HBASE-57
> I'd be also glad to get pointers to the related source code (classes).
>
> Thanks for any information,
> Naama
>
> --
> oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00 oo 00
> oo 00 oo 00 oo 00 oo 00 oo "If you want your children to be
> intelligent, read them fairy tales. If you want them to be
> more intelligent, read them more fairy tales." (Albert
> Einstein)
No virus found in this outgoing message.
Checked by AVG.
Version: 8.0.100 / Virus Database: 270.3.0/1503 - Release Date: 6/14/2008 6:02 PM