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 > > longer than for your 8G heap. > > > > St.Ack >
