What is the layout of a real Apple supplied fusion drive?
Ars Technica did an article on how to roll your own Fusion Drive and one that details the layout of an Apple installed Fusion drive from a Mac Mini.

From that article:

LeeHs-Mac-mini:~ leeh$ diskutil list
/dev/disk0
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *121.3 GB disk0
1: EFI 209.7 MB disk0s1
2: Apple_CoreStorage 121.0 GB disk0s2
3: Apple_Boot Boot OS X 134.2 MB disk0s3
/dev/disk1
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *1.0 TB disk1
1: EFI 209.7 MB disk1s1
2: Apple_CoreStorage 999.3 GB disk1s2
3: Apple_Boot Recovery HD 650.0 MB disk1s3
/dev/disk2
#: TYPE NAME SIZE IDENTIFIER
0: Apple_HFS Macintosh HD *1.1 TB disk2




LeeHs-Mac-mini:~ leeh$ diskutil cs list
    CoreStorage logical volume groups (1 found)
    |
    +-- Logical Volume Group 31CBA650-4ABC-4DA6-AA73-6D96B36693E2
        =====================================================
        Name:         Macintosh HD
        Size:         1120333979648 B (1.1 TB)
        Free Space:   0 B (0 B)
        |
        +-&lt; Physical Volume F4A50F9C-841D-4C6D-AFC4-6A10560E0717
        |   ----------------------------------------------------
        |   Index:    0
        |   Disk:     disk0s2
        |   Status:   Online
        |   Size:     120988852224 B (121.0 GB)
        |
        +-&lt; Physical Volume C86789FD-1978-453A-BCA7-81DC05AA66C7
        |   ----------------------------------------------------
        |   Index:    1
        |   Disk:     disk1s2
        |   Status:   Online
        |   Size:     999345127424 B (999.3 GB)
        |
        +-&gt; Logical Volume Family AA92FDF8-F962-4DE3-AC2F-1B6ABF22AA22
            ------------------------------------------------------
            Encryption Status:       Unlocked
            Encryption Type:         None
            Conversion Status:       NoConversion
            Conversion Direction:    -none-
            Has Encrypted Extents:   No
            Fully Secure:            No
            Passphrase Required:     No
            |
            +-&gt; Logical Volume B97C9558-14FC-4BFC-B413-AFB292BD29F0
                -----------------------------------------------
                Disk:               disk2
                Status:             Online
                Size (Total):       1115853029376 B (1.1 TB)
                Size (Converted):   -none-
                Revertible:         No
                LV Name:            Macintosh HD
                Volume Name:        Macintosh HD
                Content Hint:       Apple_HFS


As you can see, the recovery partition is "outside" the Core Storage volume which gets mounted by the OS and functions as "the Fusion Drive". The Fusion Drive is comprised of one standard partition from each disk, rather than using the full drive and storing the configuration data out of or in-band by hiding it. Everything we know so far about standard Fusion Drives is pretty straightforward and transparent.