How to determine stripe size and stripe width on HPUX 11.11 for MBRC

  • From: Lou Avrami <avramil@xxxxxxxxxxxxxx>
  • To: <hpux-admin@xxxxxxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
  • Date: Thu, 04 Sep 2008 16:49:18 -0400 (EDT)

Hello all,

I have inherited several Oracle data warehouses on HP-UX 11.11 servers, 
each 2+ TBs.  All of them are experiencing various performance issues.  

The db_multiblock_read_count (MBRC) on these databases are explicitly set to 
the value of 8.  To try to get a better idea of what we might increase the MBRC 
to, I wanted to figure out the values for the formula:

     [stripe width] x [stripe size] / [db_block_size ]

How can I determine the values for stripe width and stripe size on HP-UX 11.11?

I thought perhaps the lvdisplay command might have the info.  Looking at 
typical output, I see that there is a Stripe Size.  Would Lv Size correspond to 
the stripe width?

$ lvdisplay /dev/vgdb/lvol1
--- Logical volumes ---
LV Name                     /dev/vgdb/lvol1
VG Name                     /dev/vgdb
LV Permission               read/write   
LV Status                   available/syncd           
Mirror copies               0            
Consistency Recovery        MWC                 
Schedule                    striped      
LV Size (Mbytes)            1198080         
Current LE                  4680      
Allocated PE                4680        
Stripes                     6       
Stripe Size (Kbytes)        1024                
Bad block                   NONE         
Allocation                  strict                    
IO Timeout (Seconds)        default             

I also looked at the vgdisplay command, part of which I have included below.  
Is there something here that is the equivalent of stripe size and stripe width?

--- Volume groups ---
VG Name                     /dev/vgdb
VG Write Access             read/write     
VG Status                   available, exclusive      
Max LV                      16     
Cur LV                      5      
Open LV                     5      
Max PV                      255    
Cur PV                      36     
Act PV                      36     
Max PE per PV               65535        
VGDA                        72  
PE Size (Mbytes)            256             
Total PE                    14364   
Alloc PE                    14364   
Free PE                     0       
Total PVG                   0        
Total Spare PVs             0              
Total Spare PVs in use      0                     

   --- Logical volumes ---
   LV Name                     /dev/vgdb/lvol1
   LV Status                   available/syncd           
   LV Size (Mbytes)            1198080         
   Current LE                  4680      
   Allocated PE                4680        
   Used PV                     12      

I realize that perhaps the best way to determine the optimal MBRC value with 
these file systesm would be to use the dd command and write a large datafile 
with different block size options to the filesystems.  These database though 
have been up and running for quite a while and it's not possible to quiesce the 
systems and run benchmarks.

If anyone could confirm what I should be looking at with lgdisplay or 
vgdisplay, or can suggest another command, it would be greatly appreciated.

Lou Avrami

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