Arun's correct, on the 0.20.x and 1.x line, the CS allows "slot
reservation" based on provided memory requests from each job.
You'd have to set your cluster's maximum allowed per-task memory
request , define the per "slot" maximum memory unit , then set
on a per-job basis the real memory request you may need for it .
While the framework itself allows for memory usage monitoring in
general, CS further allows "slot management" based on the requested
resources, so if you requested a 4 GB map task memory resource  on
a cluster slot definition of 2 GB , two slots get reserved to run
such a task JVM. Arun's link has more info on setting up the whole CS.
Btw, you may also want
https://issues.apache.org/jira/browse/MAPREDUCE-3789 in your Hadoop
release/distribution since your environment is heterogenous, and the
1.x/0.20.x CS without these fixes applied might end up wasting some
cluster resources unnecessarily.
I'd also recommend looking at YARN, which is driven purely based on
resource requests (memory currently, but soon cpu and others).
 - mapred.cluster.max.map.memory.mb and mapred.cluster.max.reduce.memory.mb
 - mapred.cluster.map.memory.mb and mapred.cluster.reduce.memory.mb
 - mapred.job.map.memory.mb and mapred.job.reduce.memory.mb
On Tue, Oct 30, 2012 at 10:54 PM, Arun C Murthy <[EMAIL PROTECTED]> wrote:
> Not true, take a look at my prev. response.
> On Oct 30, 2012, at 9:08 AM, lohit wrote:
> As far as I recall this is not possible. Per job or per user configurations
> like these are little difficult in existing version.
> What you could try is to set max map per job to be say half of cluster
> capacity. (This is possible with FairSchedule, I do not know of
> For eg, if you have 10 nodes with 4 slots each. You would create pool and
> set max maps to be 20.
> JobTracker will try its best to spread tasks across nodes provided they are
> empty slots. But again, this is not guaranteed.
> 2012/10/30 Marco Zühlke <[EMAIL PROTECTED]>
>> on our cluster our jobs usually satisfied with less than 2 GB of heap
>> so we have on our 8 GB computers 3 maps maximum and on our 16 GB
>> computers 4 maps maximum (we only have quad core CPUs and to have
>> memory left for reducers). This works very well.
>> But now we have a new kind of jobs. Each mapper requires at lest 4 GB
>> of heap space.
>> Is it possible to limit the number of tasks (mapper) per computer to 1 or
>> 2 for
>> these kinds of jobs ?
> Have a Nice Day!
> Arun C. Murthy
> Hortonworks Inc.