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DanT2

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100 Posts

3846

January 7th, 2010 08:00

Powerpath pseudo devices question

I am usingPowerpath 5.2 on Solaris 10. After doing 'powermt config' , the pseudo devices for my new luns appear on 'forma't like this:

52. emcpower0g
          /pseudo/emcp@0
53. emcpower 1c
          /pseudo/emcp@1
54. emcpower 2a
          /pseudo/emcp@2

My question is how does powerpath pick which slice to use like 0g, 1c or 2a as above?  I normally put all my clariion luns on slice 7 as below.

partition> p
Current partition table (original):
Total disk cylinders available: 32766 + 2 (reserved cylinders)

Part      Tag    Flag     Cylinders         Size            Blocks
  0 unassigned    wm       0                0         (0/0/0)          0
  1 unassigned    wu       0                0         (0/0/0)          0
  2     backup    wu       0 - 32765      255.98MB    (32766/0/0) 524256
  3 unassigned    wm       0                0         (0/0/0)          0
  4 unassigned    wm       0                0         (0/0/0)          0
  5 unassigned    wm       0                0         (0/0/0)          0
  6 unassigned    wm       0                0         (0/0/0)          0
  7 unassigned    wm       0 - 32764      255.98MB    (32765/0/0) 524240

partition>

BUT on powermt display, they all show as 'a':

Pseudo name=emcpower0a
CLARiiON ID=APM00043600813 [DB01]
Logical device ID=600601609BB81000D526026545EEDE11 [LUN 77]
state=alive; policy=BasicFailover; priority=0; queued-IOs=0
Owner: default=SP A, current=SP A       Array failover mode: 1

Pseudo name=emcpower1a
CLARiiON ID=APM00043600813 [DB01]
Logical device ID=600601609BB81000D426026545EEDE11 [LUN 76]
state=alive; policy=BasicFailover; priority=0; queued-IOs=0
Owner: default=SP A, current=SP A       Array failover mode: 1


Pseudo name=emcpower2a
CLARiiON ID=APM00043600813 [DB01]
Logical device ID=600601609BB81000D326026545EEDE11 [LUN 73]
state=alive; policy=BasicFailover; priority=0; queued-IOs=0
Owner: default=SP A, current=SP A       Array failover mode: 1

is what we see on 'format' just a reference to the disk?  because not all the luns are the same, some are a , c , g...etc. These LUNS will be used for oracle ASM. In the past, I have used this and all showed up as 'a' on 'format' and 'powermt display'. This is the first time I see all of them different on the format output.

Thank you in advance.

Brion2

154 Posts

January 8th, 2010 06:00

That is correct.  From the perspective of PowerPath, we are managing the device as a whole no matter how it is carved up.

Brion2

154 Posts

January 7th, 2010 11:00

Hello.  It is not PowerPath that is picking a device and listing g, c, a slices etc.  It is the 'format' utility of the OS that did like that. PowerPath always displays the name with slice 'a' like "Pseudo name=emcpower0a" irrespective of the size of the slice. Even if the 'a' slice has been made to be zero and slice 'g' is equal to the full disk 'c' slice, "powermt display dev=0" will still show the name of the device as "emcpower0a"

It doesn't matter when it comes to the failover functionality. Failover protection is not provided for the individual slices, it is provided rather to the full device (lun) depending on the policy set for the device / storage class.

I can't say why your format utility is picking and giving different slice names. However, this display by format utility has no impact on the functionality.

Thanks.

DanT2

1 Rookie

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100 Posts

January 7th, 2010 14:00

Thanks Brion. So it does not matter what letter comes after the disk number? I can do either of these;

# newfs /dev/rdsk/emcpower0g or # newfs /dev/rdsk/emcpower0a

and it will still see the same for powerpath? I know I can do that on ...0c and will be able to mount it as such but am still confused about the rest.

Primus emc136049 deals with this issue but does not clarify it further..just says "not our fault.." ..~:)

DanT2

1 Rookie

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100 Posts

January 11th, 2010 09:00

Thanks Brion!

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