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September 10, 2005

AP and Solaris

Q: You suggested installing Solaris 8 and AP - what's with that?

A: AP (Alternate Path) was an add-on which was originally for the E10K but it became part of the operating system. In fact it should be under the 'Additional Software' section of a normal installation (the all important list that contains SunVTS). So go ahead and install the package.

To make it work you need disks which are dual connected. This is normally true of fibre channel disks and in the case of the E5500 (mentioned in the article you linked to), you would normally do this via two I/O boards. Each I/O board has two fibre links - one to each of the two A5000s. This connections will be called sf:0 and sf:1 (first I/O board), sf:2 and sf:3 (second I/O board).

Step one, is to create some ap databases (just like SVM meta databases). Organise a few tracks in a partition on at least three disks over at least two controllers (sounds just like SVM). Let's say (for arguments sake) that we have c1t0, c1t1, c2t8 and c2t9 available (in this case, connected to a D1000) where our boot disk is installed. So do the following:
# apdb -c /dev/rdsk/c1t0d0s5
# apdb -c /dev/rdsk/c2t8d0s5
...
# apconfig -D
path: /dev/rdsk/c1t0d0s5
major: 32
minor: 125
timestamp: Thursday September 11 08:00:00 EST 2001
checksum: 2211089878
corrupt: No
inaccessible: No
...
Next we need to check what disks and controllers are available (note that the output has been edited):
# apinst
sf:0
/dev/dsk/c4t0d0
/dev/dsk/c4t1d0
sf:2
/dev/dsk/c7t1d0
/dev/dsk/c7t0d0

You should check that c7t0d0 and c4t0d0 are actually the same disk (hint: look at the WWN in format). Assuming that they are the same disk:
# apdisk -c -p sf:0 -a sf:2
# apconfig -S -u
c7 sf:2
c4 sf:0 P A
metadiskname(s):
mc4t1d0 U
mc4t0d0 U
# apdb -C
We start by telling the system that sf:0 and sf:2 are related. Then we check to see that apconfig knows about our new disks. Finally we commit the changes to the database.

From here on in, we can refer to our disk (which was c4t0d0 and also c7t0d0) as mc4t1d0. The system will use both of the real paths to get to the data.

Unlike STMS, the real paths do not vanish from view so be careful to switch all references to /dev/dsk over to /dev/ap/dsk by hand.

Posted by Ozguru at September 10, 2005 06:00 AM