Try (Updated:simplified code):

#! perl -sw
use strict;

while( <DATA> ) {
    chomp;
    print "$_ ";
    unless( $. % 3 ) {
        print "\n";
    }
}

__DATA__
array A
physicaldrive 2C:1:1 port 2C:box 1:bay 1 SAS 1 TB OK
physicaldrive 2C:1:2 port 2C:box 1:bay 2 SAS 1 TB OK
array B
physicaldrive 2C:1:3 port 2C:box 1:bay 3 SAS 1 TB OK
physicaldrive 2C:1:4 port 2C:box 1:bay 4 SAS 1 TB OK
array C
physicaldrive 3C:1:5 port 3C:box 1:bay 5 SAS 1 TB OK
physicaldrive 3C:1:6 port 3C:box 1:bay 6 SAS 1 TB OK
array D
physicaldrive 3C:1:7 port 3C:box 1:bay 7 SAS 1 TB OK
physicaldrive 3C:1:8 port 3C:box 1:bay 8 SAS 1 TB OK
[download]

Ouput:

C:\test>junk
 array A physicaldrive 2C:1:1 port 2C:box 1:bay 1 SAS 1 TB OK physical
+drive 2C:1:2 port 2C:box 1:bay 2 SAS 1 TB OK
 array B physicaldrive 2C:1:3 port 2C:box 1:bay 3 SAS 1 TB OK physical
+drive 2C:1:4 port 2C:box 1:bay 4 SAS 1 TB OK
 array C physicaldrive 3C:1:5 port 3C:box 1:bay 5 SAS 1 TB OK physical
+drive 3C:1:6 port 3C:box 1:bay 6 SAS 1 TB OK
[download]