Re: [zfs-discuss] Which DTrace provider to use

[Brendan Gregg - Sun Microsystems]

G'Day Jon,                                                                      
                                                                                
On Thu, Feb 14, 2008 at 02:54:58PM -0800, Jonathan Loran wrote:                 
>                                                                               
> Hi Brendon,                                                                   
>                                                                               
> I have been using iopending, though I'm not sure how to interpret it.         
                                                                                
Did you read Examples/iopending_example.txt?  That's why it's there. :)         
                                                                                
> Is it true the column on the left is how deep in the queue requests are,      
> and then the histogram represents home many requests there are at each        
> queue depth?                                                                  
                                                                                
Yes, the counts are samples.                                                    
                                                                                
> Then I would guess if there's lots of requests with high                      
> queue depth, that's bad.                                                      
                                                                                
If it remains that way, yes.                                                    
                                                                                
>  once in awhile, I see some pretty long queues,                               
> but they only last a second, and then things even right out again.            
                                                                                
That sounds fine - operations like zil_sync() queue a bunch of I/O's            
briefly, which is usually fine.                                                 
                                                                                
Brendan                                                                         
                                                                                
--                                                                              
Brendan                                                                         
[CA, USA]
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