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HBase >> mail # user >> GC recommendations for large Region Server heaps


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Re: GC recommendations for large Region Server heaps
I see from the blog post that it is java7.  The question still stands
regarding using that with hbase, considering the open jira
https://issues.apache.org/jira/browse/HBASE-5261
On Tue, Jul 9, 2013 at 11:03 AM, Bryan Beaudreault <[EMAIL PROTECTED]
> wrote:

> @Otis, are you guys running G1GC with java6 or java7? From what I'm
> reading it seems to be more stable with better performance in java7, but I
> also believe java7 is not officially supported by apache hadoop or hbase
> yet.  I'm wondering if many people are using java7 for hbase without issue
> despite the lack of support.
>
>
> On Tue, Jul 9, 2013 at 1:52 AM, Azuryy Yu <[EMAIL PROTECTED]> wrote:
>
>> This is my HBASE GC options of CMS, it does work well.
>>
>> XX:+DisableExplicitGC -XX:+UseCompressedOops -XX:PermSize=160m
>> -XX:MaxPermSize=160m -XX:GCTimeRatio=19 -XX:SoftRefLRUPolicyMSPerMB=0
>> -XX:SurvivorRatio=2 -XX:MaxTenuringThreshold=1 -XX:+UseFastAccessorMethods
>> -XX:+UseParNewGC -XX:+UseConcMarkSweepGC -XX:+CMSParallelRemarkEnabled
>> -XX:CMSInitiatingOccupancyFraction=70 -XX:+UseCMSCompactAtFullCollection
>> -XX:CMSFullGCsBeforeCompaction=0 -XX:+CMSClassUnloadingEnabled
>> -XX:CMSMaxAbortablePrecleanTime=300 -XX:+CMSScavengeBeforeRemark
>>
>>
>>
>> On Tue, Jul 9, 2013 at 1:12 PM, Otis Gospodnetic <
>> [EMAIL PROTECTED]
>> > wrote:
>>
>> > Hi,
>> >
>> > Check
>> http://blog.sematext.com/2013/06/24/g1-cms-java-garbage-collector/
>> >
>> > Those graphs show RegionServer before and after switch to G1.  The
>> > dashboard screenshot further below shows CMS (top row) vs. G1 (bottom
>> > row).  After those tests we ended up switching to G1 across the whole
>> > cluster and haven't had issues or major pauses since.... knock on
>> > keyboard.
>> >
>> > Otis
>> > --
>> > Solr & ElasticSearch Support -- http://sematext.com/
>> > Performance Monitoring -- http://sematext.com/spm
>> >
>> >
>> >
>> > On Mon, Jul 8, 2013 at 2:56 PM, Stack <[EMAIL PROTECTED]> wrote:
>> > > On Mon, Jul 8, 2013 at 11:09 AM, Suraj Varma <[EMAIL PROTECTED]>
>> > wrote:
>> > >
>> > >> Hello:
>> > >> We have an HBase cluster with region servers running on 8GB heap size
>> > with
>> > >> a 0.6 block cache (it is a read heavy cluster, with bursty write
>> traffic
>> > >> via MR jobs). (version: hbase-0.94.6.1)
>> > >>
>> > >> During HBaseCon, while speaking to a few attendees, I heard some
>> folks
>> > were
>> > >> running region servers as high as 24GB and some others in the 16GB
>> > range.
>> > >>
>> > >> So - question: Are there any special GC recommendations (tuning
>> > parameters,
>> > >> flags, etc) that folks who run at these large heaps can recommend
>> while
>> > >> moving up from an 8GB heap? i.e. for 16GB and for 24GB RS heaps ... ?
>> > >>
>> > >> I'm especially concerned about long pauses causing zk session
>> timeouts
>> > and
>> > >> consequent RS shutdowns. Our boxes do have a lot of RAM and we are
>> > >> exploring how we can use more of it for the cluster while maintaining
>> > >> overall stability.
>> > >>
>> > >> Also - if there are clusters running multiple region servers per
>> host,
>> > I'd
>> > >> be very interested to know what RS heap sizes those are being run at
>> ...
>> > >> and whether this was chosen as an alternative to running a single RS
>> > with
>> > >> large heap.
>> > >>
>> > >> (I know I'll have to test the GC stuff out on my cluster and for my
>> > >> workloads anyway ... but just trying to get a feel of what sort of
>> > tuning
>> > >> options had to be used to have a stable HBase cluster with 16 or
>> 24GB RS
>> > >> heaps).
>> > >>
>> > >
>> > >
>> > > You hit full GC in this 8G heap Suraj?  Can you try running one
>> server at
>> > > 24G to see how it does (with GC logging enabled so you can watch it
>> over
>> > > time)?  On one hand, more heap may make it so you avoid full GC -- if
>> you
>> > > are hitting them now at 8G -- because application has more head room.
>>  On
>> > > other hand, yes, if a full GC hits, it will be gone for proportionally