LUN number to device file mapping in VA7100

[Saneesh S]

Hi All,

Can anyone tells me how the LUN number to device file mapping in VA7100 is done. Suppose I want to find out the device file for the disk having in a particular LUN number. We have got HP Command View SDM.
Thnx in advance.

Regards,
Saneesh S.

[RAC_1]

The device file mappping is as follows.

cxtxd0-cxtxd7

Then target changes. 0-7 is lun numbers.

You can run lssf on device files and check.

[Luk Vandenbussche · Accepted solution]

This is the rule

/dev/dsk/c10txdy (device file)

8*x + y = Z (LUN Z)

In your case

/dev/dsk/c10t0d0 : 8 * 0 + 0 = LUN 0
/dev/dsk/c10t0d1 : 8 * 0 + 1 = LUN 1
..
/dev/dsk/c10t0d7 : 8 * 0 + 7 = LUN 7
/dev/dsk/c10t1d0 : 8 * 1 + 0 = LUN 8

See also

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=364047

[Saneesh S]

Hi Vandenbussche,

Tnx a lot. I was looking for this answer only.

Regards,
Saneesh S.

[Bob_Vance]

Of course, this doesn't give you the X value in cXtydz.
And for each 128 LUNs, the X value changes (and it doesn't just increment -- it depends on what order the LUNs were created).

The "real" formula is
LUN# = 128*x + 8*y + z

However, the "x", here, is *not* the "X" in cXtydz (the "y" and "z" are, as stated previously).

The "x" is part of the *hardware path* of the disk in ioscan.

The actual device name can be gotten as follows:

. if the LUN was just created, execute
# ioscan
# insf -e

. # ioscan -fnCdisk >/tmp/ioscan-fnCdisk

. each group of 128 LUNs is delimited by a line for a dummy "ext_bus" with driver type "fcparray"

. the formula 128*x + 8*y + z =LUN# will give you x,y,z values that correspond to the hardware path in that ioscan output.

. the path looks something like
... disk 91 0/2/1/0.1.0.0.x.y.z
so search for disk.*x\.y\.z

. the line after the matching HW path give you the actual device name:
... /dev/dsk/c32t2d0 /dev/rdsk/c32t2d0

If you have multiple HBA paths to the array then you will have 2 hardware paths and device names for the LUN.

If you have multiple arrays, then it is even more complicated -- you must also match the beginning part of the disk hardware path to the hardware path of the particular array.


hth
bv

[Uday_S_Ankolekar]

I would use armtopology command. It will give you all the details related to device name, LUN , Hosts etc
armtopology is in /opt/sanmgr/commandview/client/sbin directory

-USA

[Bob_Vance]

Hi, Uday

>I would use armtopology command.

Well sure, if you want to do it the *easy* way ;>)

However, 'armtopology' doesn't give the array name, so, in a multiple-array environment, you still have to somehow match it to an array.

There doesn't seem to be a way, a priori, to determine the particular array HW path in a multi-path, multi-array environment. I suspect that 'armtopology' is basically doing what I outlined manually -- I notice that there are various ioscan-like outputs in the /var/opt/sanmgr.

One way would be to create LUN0 in each array as a different size when first setting up the arrays. Another way, is to document the arrays' HW path when first setting it up. Another way would be to create a new temp LUN on a particular array and then see on which HW path it shows up.

BTW,
LUNs don't have to be created sequentially, so the situation where LUN# > 128 can easily arise. E.g., create LUNs above 500 as scratch LUNs, or whatever.


bv