Archive for November, 2014

NetApp LUN Serial and SCSI Word 83

Sunday, November 2nd, 2014

I was wandering for a long while about the connection between NetApp’s LUN Serial and the identifier the host sees, aka “Word 83”. There was an obvious connection, but I figured it out only today.

The LUN Serial is an ASCII representation of the hexadecimal Word 83, or, to be exact, the last 22 hex characters of it.
See:

lun serial /vol/volume/qtree/lun
Serial#:  7S1PW?Bym7B

When querying the multipath device represented there, we get:

360a9800037533150573f4279316d3742 dm-7 NETAPP,LUN
[size=4.0T][features=0][hwhandler=0][rw]
_ round-robin 0 [prio=4][active]
 _ 1:0:0:30 sdm  8:192  [active][ready]
 _ 2:0:0:30 sdz  65:144 [active][ready]

Using a simple web calculator of Hex-to-Text (example: Use this), we can see that 7S1PW?Bym7B is translated to
37533150573f42796d3742 , which represents the last 22 characters of the reported Word 83. I assume that the leftmost nine hex characters represent the storage device. So, easy to identify.

An additional nice trick is to ask the NetApp to represent the LUN Serial in hex:

lun serial -x /vol/volume/qtree/lun
Serial (hex)#: 0x37533150573f4279316d3742

which represents the same Word 83 we’ve seen before. However, NetApp will not allow you to set (under priv mode) the LUN Serial directly to a hex value. There comes the importance of the Hex-to-Text calculation tools.