[Pvfs2-users] metadata

[Sam Lang]

On Feb 2, 2007, at 4:15 PM, Sam Lang wrote:

>
> On Feb 2, 2007, at 3:28 PM, Steve wrote:
>
>> Hi,
>>
>> Is there any rough rule of thumb guide for the size of the  
>> metadata for the
>> size of the store ?
>
> Hi Steve,
>
> The size of the metadata as a percent of the size of the storage  
> space depends on the sizes of the files.  I'm doing a back of the  
> envelope calculation, but I think that in general, each file takes  
> up somewhere around 650 bytes to store its metadata, while  
> directories are a little less (maybe 500 bytes).  Remember though  
> that the metadata size changes for different configurations (more  
> servers, etc.).  There's also overhead related to the storage space  
> itself, which is about (100K * numservers).  If you know how many  
> files/directories you have in your volume, you should be able to  
> get a rough estimate of your metadata size using those numbers above.

I should clarify though, that the filesystem size (capacity and  
available) reported by df for PVFS volumes is just the sum of the  
sizes on each of the IO servers (capacity is actually the min of all  
servers * numservers).  This means that what df reports in terms of  
usage can be inaccurate if the PVFS storage on the IO nodes is shared  
with other files.

-sam


> -sam
>
>
>>
>> Steve
>>
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>