[Pvfs2-developers] Distribution by hostname

[Bradley W Settlemyer]

Sam Lang wrote:
> 
>> How about just add PVFS_sys_dist_get_IO_server_aliases() and
>> PVFS_sys_dist_set_IO_server_mapping().  Under the hood each
>> distribution orders the IO servers it'll use according to the
>> mapping then does business as usual.  This instead of the random
>> starting point and sequential ordering used now.
> 
> What are the benefits of those functions over something like:
> 
> PVFS_sys_dist_set_param(..., "io-server-mapping", &server_map);
> 
> I dislike the idea of adding interfaces that won't get much use, esp if 
> we already have a generic mechanism for doing the same.
> 
> -sam

Just so we're all clear on what was intended with that interface, the 
idea is that distributions can overload the behaviour of the underlying 
parameter setter.

For example, in the default provided functions, I checked the data for 
overrun of the distribution data type, but it doesn't have any support 
for an underfilled data type (for example, if an int is set into an 
int64, that's probably going to lead to 32 bits of random junk in the 
distribution parameter).  But that will work fine (though perhaps 
precariously) for the default simple-stripe distribution.

The varstrip guys provided a parameter setter that parsed some a string 
format.  So the current model is that each distribution provides its own 
string format.  I'm not sure whether that's really the best approach or not.

Cheers,
brad