How to put Oracle Redo Log file at the outer edge of disk for performance?
Oracle redo files are written in a sequential fashion. This is what gives the best performance because the write head is always on the correct location to write again, as long as the disk is not shared with other files. As soon as the disk - or more precisely - the write head is shared with a datafile, the head has to make more movements to satisfy the random IO pattern that is mostly found for datafiles.

The cylinders numbering of disks start at the outer edge of the disk. See Oracle Solaris 11 System Administration: Administering Storage Devices for some info. While formatting the slices you can point them their location on disk.

If you really want high performant redo files, give them their own dedicated disks and stripe them for best performance. Don't forget that the archiver is also going to read the redo after it has been completed ....

Managing files on separate disks is something of the past. Since years Oracle preaches SAME. Stripe And Mirror Everything. See Optimals Storage Configuration Made Easy Add the disks to an ASM diskgroup and let ASM handle the file placement.