-Re: HDFS / Federated HDFS - Doubts
Suresh Srinivas 2013-10-16, 17:48
On Wed, Oct 16, 2013 at 9:22 AM, Steve Edison <[EMAIL PROTECTED]> wrote:
> I have couple of questions about HDFS federation:
> Can I state different block store directories for each namespace on a
> datanode ?
No. The main idea of federation was not to physically partition the storage
across namespace, but to use all the available storage across the
namespaces, to ensure better utilzation.
> Can I have some datanodes dedicated to a particular namespace only ?
As I said earlier, all the datanodes are shared across namespaces. If you
want to dedicate datanodes to a particular namespace, you might as well
create it as two separate clusters with different set of datanodes and a
> This seems quite interesting. Way to go !
> On Tue, Oct 1, 2013 at 9:52 PM, Krishna Kumaar Natarajan <[EMAIL PROTECTED]
> > wrote:
>> Hi All,
>> While trying to understand federated HDFS in detail I had few doubts and
>> listing them down for your help.
>> 1. In case of *HDFS(without HDFS federation)*, the metadata or the
>> data about the blocks belonging to the files in HDFS is maintained in the
>> main memory of the name node or it is stored on permanent storage of the
>> namenode and is brought in the main memory on demand basis ? [Krishna]
>> Based on my understanding, I assume the entire metadata is in main memory
>> which is an issue by itself. Please correct me if my understanding is wrong.
>> 2. In case of* federated HDFS*, the metadata or the data about the
>> blocks belonging to files in a particular namespace is maintained in the
>> main memory of the namenode or it is stored on the permanent storage of the
>> namenode and is brought in the main memory on demand basis ?
>> 3. Are the metadata information stored in separate cluster
>> nodes(block management layer separation) as discussed in Appendix B of this
>> document ?
>> 4. I would like to know if the following proposals are already
>> implemented in federated HDFS. (
>> - Separation of namespace and block management layers (same as qn.3)
>> - Partial namespace in memory for further scalability
>> - Move partial namespace from one namenode to another
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