why do front end director ports WWN does not change after replacement in symmetrix?

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why do front end director ports WWN does not change after replacement in symmetrix?

vmax_fa_all1

 

 

 

This question used to bother me for long time.I used to answer myself like their must be some mechanism EMC is using to get same WWN as old director port to even new director after replacement.Recently I found a primus which helped me to understand deep down on FA WWN.

I will follow the primus emc223285 and try decode Symmetrix WorldWide Names (WWNs) on a VMAX.

We will be using the following WWN as an example: 50000972081349AD

5000097-these hexa numbers are assigned by IEEE and is the vender UID of Symmetrix V-Max.so these
numbers same for any FA WWN of VMAX array.

now let us break down reamaining WWN 2081349AD.
Start by breaking down the hexadecimal digit WWN into binary.

2         0        8        1        3       4        9       A      D
0010 0000 1000 0001 0011 0100 1001 1010 1101

bit35 <—————————————–< bit 0

Starting from left to right, number the bits from 35 on down to 0.

Follow below screenshot along with descritpion to undesrtand well.

bit

 

Bit arrangement description:

Bits 35 through 33:Bits 35 through 33 deal with the build location of the array.  For any given WWN, one of the 3 bits will be set; the other two bits will be not be set.  If bit 35 is set, the array was made in China and the Serial Number starts with CN49xxxxxxx.  If bit 34 is set, the array was made in Europe and the Serial Number starts with CK29xxxxxxx.  Lastly if bit 33 is set, the array was made in the USA and the Serial Number starts with HK19xxxxxxx. In the example provided, bit 33 is set, which indicates the example WWN has a Serial Number starting in HK19xxxxxxx.

Bits 32 through 26:bits 32 through 26, deal with the Symmetrix Model Type.
Refer to the following chart for a breakdown of the bits.

bit 32 26

 

 

 

 

 

In the example WWN, the break down of bits 32 through 26 is 0 0 0 0 0 1 0 which indicates the WWN is HK1926xxxxx.

Bits 25 through 10:Bits 25 through 10 encode the last 5 digits of the Symmetrix Serial Number.  Take those bits and place them into a scientific calculator set to binary, convert the binary into decimal, and you will receive the last 5 digits of the Symmetrix Serial Number.  In the example, bits 26 through 10 come out to be 000 0001 0011 0100 10.  Placing this into a calculator and converting from binary to decimal yields 1234.  If the yield comes out to be a 4-digit number, front pad the number with a 0 to make 5 digits (i.e., 01234). The full Serial Number for the Symmetrix in the example WWN is HK192601234.

binarydecimal

 

 

 

 

 

Bits 9 through 6:  Bits 9 through 6 hold the encoding for the processor letter (CPU letter) for the director.  Use the break out of the bits to the chart below.

bit 9 6

 

Bits 5 through 2: Bits 5 through 2 hold the encoding for the director number for the director.  Use the break out of the bits to the chart below.

bit52

 

the last two bits:Lastly, the last two bits, bits 1 and 0, hold the encoding for the director port.  If the bits are 00, then it is the 0 or A port. If the bits are 01, then it is the 1 or B port.  In the example, it is port 1 or B.

So, finally, WWN 50000972081349AD decodes to VMAX / VMAX 20K HK192601234 director 12g port 1/B 🙂

 

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what is Inquiry utility (INQ)?

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So what is INQ?

Inquiry utility (INQ) is a command-line troubleshooting utility that displays information on storage devices, typically Symmetrix. By default, INQ returns the device name, Symmetrix ID, Symmetrix LUN, and capacity. This utility will operate independently of any other EMC software.Use the INQ Utility to collect system information to provide to EMC Global Services for problem troubleshooting.

But we generally use EMC grab report for that?

Yes ,even INQ is also one of several tools bundled and run as part of the host grab utilities (EMC Grab and EMCReports).

 Can we analyze INQ output?

Luckily we can analyze INQ output. below is the process. Generally we see two types of INQ output. It is Enginuity level dependent.

for older versions INQ output will be in below format

When running inq or syminq, you’ll see a column titled Ser Num. This column has quite a bit of information hiding in it.

Device                          Product                         Device

—————-        ————————-       ——————————–

Name                    Type    Vendor  ID              Rev     Ser Num         Cap(KB)

—————-        —–   ——- ———       ——- ———       ——–

/dev/dsk/c1t0d0                 EMC     SYMMETRIX       5265    73009150        459840

/dev/dsk/c1t4d0         BCV     EMC     SYMMETRIX       5265    73010150        459840

/dev/dsk/c1t5d0         GK      EMC     SYMMETRIX       5265    73019150        2880

/dev/dsk/c2t6d0         GK      EMC     SYMMETRIX       5265    7301A281        2880

Using the first and last serial numbers as examples, the serial number is broken out as follows:

73      Last two digits of the Symmetrix serial number

009     Symmetrix device number

15      Symmetrix director number. If <= 16, using the A processor

0       Port number on the director

 

If Device Serial Number = “71018000” Legend = SSVVVDDP

SS = Last 2 Digits of System S/N V = Volume Number (000 – FFF) DD = Director Number (01 – 16 is A director, 17 – 32 is B

director) P = Port (0 – 3)

 

In new INQ outputs generally we can directly find columns for array SN and  device id and device WWN(i don’t have inq output from newe version so not posting it here)

 

what if I don’t have INQ utility and can get only multipathing output?

Yes. if mutlipathing output is from powerpath then we can directly get most of details

 

#powermt display dev=all ====>  Display All Attached LUNs

 

Mostly we used to run this command powermt, which will display all the attached logical devices to the server.

 

Pseudo name=disk915

Symmetrix ID=000290103691

Logical device ID=06B8

state=alive; policy=SymmOpt; priority=0; queued-IOs=0;

==============================================================================

————— Host —————   – Stor –   — I/O Path —  — Stats —

###  HW Path               I/O Paths    Interf.   Mode    State   Q-IOs Errors

==============================================================================

3 0/4/0/0/0/1.0x5006048c52a862e7.0x40a6000000000000 c14t4d6   FA  8cB   active  alive       0      2

3 0/4/0/0/0/1.0x5006048c52a862f7.0x40a6000000000000 c15t4d6   FA  8dB   active  alive       0      2

5 0/5/0/0/0/1.0x5006048c52a862e8.0x40a6000000000000 c16t4d6   FA  9cB   active  alive       0      2

5 0/5/0/0/0/1.0x5006048c52a862f8.0x40a6000000000000 c17t4d6   FA  9dB   active  alive       0      2

 

If I have only native multipathing?

So now we have to use a bit of technique to decode  device WWN which is part of CTD addressing

General EMC device  WWN: 600009700001926055542533030363338

you can break above wwn this way 60000970000 192605542 5330 30363338

192605542-serial nuumber of array in decimal

last 8 digits-30363338 are the symm device in ASCII

ASCII to Hexa

30=0

36=6

33=3

38=8

so device is 0638

so now we can say device is 0638 from array 5542

where exactly I can use this INQ or multipathing output ?

These outputs will be helpful for us in knowing what storage devices server able to see from san side. this can help us in resolving device missing or path down tickets.

 where do I get INQ utility?

Below is the FTP link

INQ utility

what else?

Yup, I am done :). If you have more info or any corrections please feel free to mail me..