change scsi chain instance

[Lorenzo Facello]

Hi all,
can I change my scsi chain where I have disks
ex. c13t4dx
into ex. c9t4dx

Thanks

[Patrick Wallek]

Check out the following document from the Technical Knowledge Base:

Doc ID KBRC00004879
http://www1.itrc.hp.com/service/cki/docDisplay.do?docLocale=en_US&docId=200000069332604

[Jean-Louis Phelix]

Hi,

You should perhaps call it instance number ? To do it, you have to use ioinit (the man page is really clear about creating an very simple input file for ioinit). Man ioinit ...

Basically :

- grep ext_bus in ioscan -kfn

ie "ext_bus 13 0/0/2/1 ..."

- check that no "ext_bus 9 xxx" already exists (if yes then add another line to remap instance 9 to another number)

- create a file like :

0/0/2/1 ext_bus 13

- use

ioinit -f infile

- check for errors and reboot if ok

You should be aware that your lvmtab could be impacted by this ...

Regards.

[Steven E. Protter]

depending on the disk, thats usually done by shutting down the system and changing the dip switches on the back of the disk array(HP-6000) for example.

You need to know what settings you get off the dip switches

4321

if 4 is up and every other switch is down, you get scsi id 4 if 1 is clicked up, you get id 5. c5d4dx

Get the picture?

SEP

[Patrick Wallek]

You are talking about the SCSI ID (the t part in c?t?d?), Steven. Lorenzo, I think, is asking about how to change the controller instance number (the c part in c?t?d?) which isn't nearly as easy.

[Bill Hassell]

The instance number (c13 and c9 in your example) is the driver's view of the hardware path. The minor number in the devicefile isn't nearly large enough to hold typical hardware paths, so each new SCSI card gets the next number starting at zero (c0). After months of changing the system around, you may want to have a more consistent naming convention, but this can be inherently dangerous to the health of your system.

If these disks have never been used, you can try the example given in the knowledge base tech-note. But if these disks are already part of a volume group, then the volume group will unuseable once these devicefiles are renamed. They are coded into the binary file /etc/lvmtab. Now you could first vgexport the volume group, try renumbering the devicefiles with the ioinit file and then re-import the volume group. However, the risk is far too high just to have the instance numbers look pretty or match another system.