Hello,

I would like to ask if I can do the following. Assuming that I have a
datanode, i.e., dn1, which already contains some useful blocks. Here,
I do not want to save new data blocks to the datanode, but I still
want to use the blocks that already exist in the datanode (dn1).
I considered to use exclude file (dfs.hosts.exclude). However, if I
add "dn1" to the exclude file list, I cannot use blocks that are
already contained in dn1. If it is right, can you please give me some
guidances to do what I'm thinking using HDFS?

Thanks,

Kyungyong Lee,

One way: This may be possible to do if you inflate the
"dfs.datanode.du.reserved" property on the specific DataNode to a very
large bytes value (> maximum volume size). This way your NN will still
consider the DN as a valid one that carries readable blocks, but when
writing files this DN will never be selected due to its
false-lack-of-space report.

On Mon, May 21, 2012 at 12:37 AM, Kyungyong Lee <[EMAIL PROTECTED]> wrote:
> Hello,
>
> I would like to ask if I can do the following. Assuming that I have a
> datanode, i.e., dn1, which already contains some useful blocks. Here,
> I do not want to save new data blocks to the datanode, but I still
> want to use the blocks that already exist in the datanode (dn1).
> I considered to use exclude file (dfs.hosts.exclude). However, if I
> add "dn1" to the exclude file list, I cannot use blocks that are
> already contained in dn1. If it is right, can you please give me some
> guidances to do what I'm thinking using HDFS?
>
> Thanks,

--
Harsh J

Thank you very much for the answer, Harsh J. Your suggestion totally
makes sense, and I can do what I wanted :)

Best,

On Sun, May 20, 2012 at 10:53 PM, Harsh J <[EMAIL PROTECTED]> wrote:
> Kyungyong Lee,
>
> One way: This may be possible to do if you inflate the
> "dfs.datanode.du.reserved" property on the specific DataNode to a very
> large bytes value (> maximum volume size). This way your NN will still
> consider the DN as a valid one that carries readable blocks, but when
> writing files this DN will never be selected due to its
> false-lack-of-space report.
>
> On Mon, May 21, 2012 at 12:37 AM, Kyungyong Lee <[EMAIL PROTECTED]> wrote:
>> Hello,
>>
>> I would like to ask if I can do the following. Assuming that I have a
>> datanode, i.e., dn1, which already contains some useful blocks. Here,
>> I do not want to save new data blocks to the datanode, but I still
>> want to use the blocks that already exist in the datanode (dn1).
>> I considered to use exclude file (dfs.hosts.exclude). However, if I
>> add "dn1" to the exclude file list, I cannot use blocks that are
>> already contained in dn1. If it is right, can you please give me some
>> guidances to do what I'm thinking using HDFS?
>>
>> Thanks,
>
>
>
> --
> Harsh J