FAST Cache Setup (2 or 4)

it will automatically create 2 x RAID1 sets

here i have 4 disks used for FAST Cache

 
 
 
 
 
 
 
 
 
 
 
 

  
  

   
   

    
    
RaidGroup ID:                          
    
    
498
   
   
   
   

    
    
RaidGroup Type:                        
    
    
r1
   
   
   
   

    
    
RaidGroup State:                       
    
    
Explicit_Remove
   
   
   
   

    
    


    
    
Valid_luns
   
   
   
   

    
    
List of disks:                         
    
    
Bus 0 Enclosure 0  Disk 5
   
   
   
   

    
    


    
    
Bus 0 Enclosure 0  Disk 4
   
   
   
   

    
    
List of luns:                          
    
    
8181 8180 8179 8178
   
   
   
   

    
    
Max Number of disks:                   
    
    
2
   
   
   
   

    
    
Max Number of luns:                    
    
    
256
   
   
   
   

    
    
Raw Capacity (Blocks):                 
    
    
761499648
   
   
   
   

    
    
Logical Capacity (Blocks):             
    
    
380749824
   
   
   
   

    
    
Free Capacity (Blocks,non-contiguous): 
    
    
0
   
   
  
  
 
 
Free contiguous group of unbound segments: 0
 
 
 
 
 
 
 
 
 
 
 
 

  
  

   
   

    
    
Defrag/Expand priority:                
    
    
Medium
   
   
   
   

    
    
Percent defragmented:                  
    
    
100
   
   
   
   

    
    
Percent expanded:                      
    
    
N/A
   
   
   
   

    
    
Disk expanding onto:                   
    
    
N/A
   
   
   
   

    
    
Lun Expansion enabled:                 
    
    
NO
   
   
   
   

    
    
Legal RAID types:                      
    
    
r1
   
   
   
   

    
    
Is Private:                            
    
    
YES
   
   
  
  
 
 
*******************************************************************************
 
 
 
 
 
 
 
 
 
 
 
 

  
  

   
   

    
    
RaidGroup ID:                          
    
    
499
   
   
   
   

    
    
RaidGroup Type:                        
    
    
r1
   
   
   
   

    
    
RaidGroup State:                       
    
    
Explicit_Remove
   
   
   
   

    
    


    
    
Valid_luns
   
   
   
   

    
    
List of disks:                         
    
    
Bus 0 Enclosure 0  Disk 7
   
   
   
   

    
    


    
    
Bus 0 Enclosure 0  Disk 6
   
   
   
   

    
    
List of luns:                          
    
    
8185 8184 8183 8182
   
   
   
   

    
    
Max Number of disks:                   
    
    
2
   
   
   
   

    
    
Max Number of luns:                    
    
    
256
   
   
   
   

    
    
Raw Capacity (Blocks):                 
    
    
761499648
   
   
   
   

    
    
Logical Capacity (Blocks):             
    
    
380749824
   
   
   
   

    
    
Free Capacity (Blocks,non-contiguous): 
    
    
0
   
   
  
  
 
 
Free contiguous group of unbound segments: 0
 
 
 
 
 
 
 
 
 
 
 
 

  
  

   
   

    
    
Defrag/Expand priority:                
    
    
Medium
   
   
   
   

    
    
Percent defragmented:                  
    
    
100
   
   
   
   

    
    
Percent expanded:                      
    
    
N/A
   
   
   
   

    
    
Disk expanding onto:                   
    
    
N/A
   
   
   
   

    
    
Lun Expansion enabled:                 
    
    
NO
   
   
   
   

    
    
Legal RAID types:                      
    
    
r1
   
   
   
   

    
    
Is Private:                            
    
    
YES
   
   
  
  
 
 

What I'm trying to figure it out is if I should select 2 or 4 drives.

I'm going to dedicate all 4.

I was confused whether to choose 2 or 4 drives from the dropdown box.

I didn't know if there are any performance considerations choosing one option or the other.

by the way did you see recommendation that if you have 2 or 4 drives:

As a general rule, when configuring FAST Cache, make sure all of the drives involved are either entirely contained within enclosure 0_0 (only recommended for 2 or 4 drive FAST Cache configurations) or entirely in enclosures other than 0_0.  Either of these recommended configurations will not result in unnecessary rebuilds upon array power-downs.  Please see emc285141 for further information about the use of Bus 0 Enclosure 0.

you mean how many drives you want to dedicate for Fast Cache ?

Hello dynamox,

I have the option to select 2 or 4 disks when creating the FAST Cache.

See attached picture.

Thanks!

cool, none of the drives are in DAE 0_0

Just select the number of drives and let the array do the magic. You can run "naviseccli -h getrg -messner" to see how it picked the devices. I bet you one pair will be two disks on bus 1 and the other pair on bus 3.

How did you find out?

arrh..sorry, you have to add all 4 drives at the same time.

i guess to ensure that raid1 set is spread over two buses you can select to add 2 drives first and manually add one drive from bus 1 and bus 3. Hit ok and let it build the pair. Then repeat the steps with the other 2 drives but this time add drive from bus 3 firsta and then the one from bus 1.

Message was edited by: dynamox

in order to increase Fast Cache you have to destroy existing Fast Cache configuration and reconfigure it from scratch with additional disks. I am trying that right now, i want to see how my selection of disks in Unisphere will reflect the actual r1 pairing.

i can't figure out in Unisphere how to manualy select 4 drives to be used for Fast Cache and control which drive is primary and secondary, so i just did it from the command line:

naviseccli -h cache -fast -create -disks 0_0_7 0_0_4 0_0_5 0_0_6 -mode rw -rtype r_1

in your case if you want to select primary and secondary on different buses you would:

naviseccli -h cache -fast -create -disks 1_1_x 3_1_x 3_1_x 1_1_x -mode rw -rtype r_1

i put "x" where the drive number is supposed to be as i can't tell what it is from your screenshot.

Do you think is better to split the mirrors in buses rather than a mirror per bus?

In other words, having:

1_1_13

3_1_13    

1_1_14

3_1_14

is better than

1_1_13

1_1_14

3_1_13

3_1_14

or the end result is irrelevant?

You are absolutely right!

Thank you very much from your time and help.

Manuel.