Keep in mind:
There are
two levels of partitioning for OpenBSD:
MBR partitions (on MBR architectures)
Disklabel partitions.
One primary MBR partition is used for
all space to be used by OpenBSD. Within that partition -- the area of the drive usable by OpenBSD -- you may have up to 16 disklabel partitions, specified by letter: "a" through "p". (Partition "c" is special, it is the entire physical drive.)
On OpenBSD, the fdisk(8) program is used to manage MBR partitions, and the disklabel(8) program is used to manage disklabels.
*IF* you do not move the MBR partition, and *IF* you do not damage or destroy the information in "/data", and *IF* you have not destroyed the disklabel or you have a backup of that disklabel, then the information in "/data" will still be good.