Mailing-List: contact issues-help@hbase.apache.org; run by ezmlm
Precedence: bulk
Date: Mon, 21 May 2012 02:27:41 +0000 (UTC)
From: "Li Pi (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <741262909.2168.1337567261551.JavaMail.jiratomcat@issues-vm>
In-Reply-To: 
 <529070215.19745.1334269158397.JavaMail.tomcat@hel.zones.apache.org>
Subject: [jira] [Commented] (HBASE-5778) Turn on WAL compression by default
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


    [ https://issues.apache.org/jira/browse/HBASE-5778?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13279927#comment-13279927 ] 

Li Pi commented on HBASE-5778:
------------------------------

How far can replication lag behind our writes? If we can guarantee that an entry won't be evicted before replication, we can simply consult the main dictionary to decompress it.
                
> Turn on WAL compression by default
> ----------------------------------
>
>                 Key: HBASE-5778
>                 URL: https://issues.apache.org/jira/browse/HBASE-5778
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Jean-Daniel Cryans
>            Assignee: Lars Hofhansl
>            Priority: Blocker
>         Attachments: 5778-addendum.txt, 5778.addendum, HBASE-5778.patch
>
>
> I ran some tests to verify if WAL compression should be turned on by default.
> For a use case where it's not very useful (values two order of magnitude bigger than the keys), the insert time wasn't different and the CPU usage 15% higher (150% CPU usage VS 130% when not compressing the WAL).
> When values are smaller than the keys, I saw a 38% improvement for the insert run time and CPU usage was 33% higher (600% CPU usage VS 450%). I'm not sure WAL compression accounts for all the additional CPU usage, it might just be that we're able to insert faster and we spend more time in the MemStore per second (because our MemStores are bad when they contain tens of thousands of values).
> Those are two extremes, but it shows that for the price of some CPU we can save a lot. My machines have 2 quads with HT, so I still had a lot of idle CPUs.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira