-Re: NameNode heapsize
Edward Capriolo 2011-06-10, 14:00
On Fri, Jun 10, 2011 at 8:22 AM, Brian Bockelman <[EMAIL PROTECTED]>wrote:
> On Jun 10, 2011, at 6:32 AM, [EMAIL PROTECTED] wrote:
> > Dear all,
> > I'm looking for ways to improve the namenode heap size usage of a
> 800-node 10PB testing Hadoop cluster that stores
> > around 30 million files.
> > Here's some info:
> > 1 x namenode: 32GB RAM, 24GB heap size
> > 800 x datanode: 8GB RAM, 13TB hdd
> > *33050825 files and directories, 47708724 blocks = 80759549 total. Heap
> Size is 22.93 GB / 22.93 GB (100%) *
> > From the cluster summary report, it seems the heap size usage is always
> full but couldn't drop, do you guys know of any ways
> > to reduce it ? So far I don't see any namenode OOM errors so it looks
> memory assigned for the namenode process is (just)
> > enough. But i'm curious which factors would account for the full use of
> heap size ?
> The advice I give to folks is to plan on 1GB heap for every million
> objects. It's an over-estimate, but I prefer to be on the safe side. Why
> not increase the heap-size to 28GB? Should buy you some time.
> You can turn on compressed pointers, but your best bet is really going to
> be spending some more money on RAM.
The problem with the "buy more RAM" philosophy is the JVM's tend to have
problems operating without pausing for large heaps. NameNode JVM pausing is
not a good thing. Number of Files and Number of Blocks is important so
larger block sizes help make for less NN memory usage.
Also your setup nodes do not mention a secondary name node. Do you have one?
It needs slightly more RAM then the NN.