[Pvfs2-developers] How does PVFS2 manage the free space?

[Sam Lang]

On Oct 20, 2006, at 4:47 PM, Peng Gu wrote:

> My question is that, when PVFS2 create a new file, does the metadata
> server (MDS) know that there are enough free space on the I/O node for
> this new file? In other words, does the MDS have to check the free
> space on each I/O node on every file creation? Are there any potential
> performance issues here?
>

Hi Peng,

Every file creation does go to the IO nodes to allocate the datafile  
handles, so the check for free space does occur.  Because of this  
allocation on the IO servers, the performance of file creation will  
be slower than if it were to just go directly to the metadata server.

At some point we will probably implement batch allocation of datafile  
handles, and at that point creates will be able to just go to the  
metadata server, but as you can probably imagine, this will prevent  
us from doing the disk space checking that we get with the present  
create scheme.

-sam

> Thanks,
> Peng
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