FusionDrive seems to not use SSD

Question

I'm trying to make a homebrew FD of 500GB HDD and 128GB SSD. I'm using Maverics 10.9.1 and MD101 MBP.

What I did was:

1. install HDD into superdrive bay
2. install SSD into HDD compartment
3. use diskutil cs convert on HDD to make it a CoreStorage Logical volume
4. add SSD into the logical volume with diskutil cs addDisk
5. resize Logical volume to use all available space on both SSD and HDD with diskutil cs resizeVolume

What I can see now is a volume that has a capacity of summary capacity of SSD and HDD, but iostat shows that SSD load is zero. No matter what I'm doing - copying files around, downloading new files, etc. it remains zero (here disk0 is my SSD, disk1 is HDD and disk3 is a USB drive with TimeMachine backups):

          disk0           disk1           disk3       cpu     load average
KB/t tps  MB/s     KB/t tps  MB/s     KB/t tps  MB/s  us sy id   1m   5m   15m
0.00   0  0.00     0.00   0  0.00     0.00   0  0.00   1  2 96  1.08 1.32 1.13
0.00   0  0.00     0.00   0  0.00     0.00   0  0.00   1  1 98  1.08 1.32 1.13
0.00   0  0.00   114.00   2  0.22     0.00   0  0.00   6  3 91  1.08 1.32 1.13
0.00   0  0.00     9.24  29  0.26     0.00   0  0.00   8  5 87  1.08 1.32 1.13
0.00   0  0.00     8.62  65  0.54     0.00   0  0.00   8  5 87  1.08 1.32 1.13
0.00   0  0.00     9.65  88  0.83     0.00   0  0.00  26  9 64  1.08 1.32 1.13
0.00   0  0.00     3.96  78  0.30     0.00   0  0.00  28  2 70  1.07 1.31 1.13
0.00   0  0.00    20.65  94  1.89     0.00   0  0.00  19  4 77  1.07 1.31 1.13
0.00   0  0.00    12.96  47  0.59     0.00   0  0.00  17 11 73  1.07 1.31 1.13
0.00   0  0.00    51.02  89  4.43     4.00   1  0.00  12 12 77  1.07 1.31 1.13
0.00   0  0.00    15.78 148  2.28     0.00   0  0.00  16 10 74  1.07 1.31 1.13
0.00   0  0.00    14.02 273  3.74     0.00   0  0.00   7  4 89  1.06 1.31 1.13
0.00   0  0.00    16.17 146  2.30     0.00   0  0.00   8  5 86  1.06 1.31 1.13
0.00   0  0.00     0.00   0  0.00     0.00   0  0.00   1  1 97  1.06 1.31 1.13
0.00   0  0.00     0.00   0  0.00     0.00   0  0.00   1  1 98  1.06 1.31 1.13
0.00   0  0.00     0.00   0  0.00     0.00   0  0.00   5  3 91  1.06 1.31 1.13
0.00   0  0.00     0.00   0  0.00     0.00   0  0.00   2  2 96  0.98 1.28 1.12
0.00   0  0.00    12.00   5  0.06     0.00   0  0.00   2  2 96  0.98 1.28 1.12
0.00   0  0.00    31.00   4  0.12     0.00   0  0.00   2  3 95  0.98 1.28 1.12
0.00   0  0.00    52.00   1  0.05     0.00   0  0.00   5  4 91  0.98 1.28 1.12

diskutil cs list:

CoreStorage logical volume groups (1 found)
|
+-- Logical Volume Group 8ACC1316-4CD3-44F4-AC77-E6DBB9E8FDCC
    =========================================================
    Name:         Macintosh HD
    Status:       Online
    Size:         626939805696 B (626.9 GB)
    Free Space:   1335816192 B (1.3 GB)
    |
    +-< Physical Volume 1BACBF70-83E2-47C2-9EE1-672920B6CB75
    |   ----------------------------------------------------
    |   Index:    0
    |   Disk:     disk1s2
    |   Status:   Online
    |   Size:     499248103424 B (499.2 GB)
    |
    +-< Physical Volume DDD92F99-310F-4204-9C3E-B4EFC8A2C0E6
    |   ----------------------------------------------------
    |   Index:    1
    |   Disk:     disk0s2
    |   Status:   Online
    |   Size:     127691702272 B (127.7 GB)
    |
    +-> Logical Volume Family 0062228C-F252-4261-85FB-D595D0EA9BC5
        ----------------------------------------------------------
        Encryption Status:       Unlocked
        Encryption Type:         None
        Conversion Status:       NoConversion
        Conversion Direction:    -none-
        Has Encrypted Extents:   No
        Fully Secure:            No
        Passphrase Required:     No
        |
        +-> Logical Volume 93ADABE5-D785-4519-8435-8B5EC7D904B0
            ---------------------------------------------------
            Disk:                  disk2
            Status:                Online
            Size (Total):          624999997440 B (625.0 GB)
            Conversion Progress:   -none-
            Revertible:            No
            LV Name:               Macintosh HD
            Volume Name:           Macintosh HD
            Content Hint:          Apple_HFS

Don't think that it's normal, but who knows. Has anyone faced such problem? What have I done wrong?

Answer 1

Can confirm it's the order of HDD-SSD! I have the same issue on my MBP 13" 9.2

Usually, the instructions assume that you disk0 is the HDD and disk1 the SSD. This should be the case 99% of times, but not in mine (just like with yours).

The DVD-Replacement Hard Disk Caddy I bought only supported SATA2 not SATA3, which caused random errors with the SSD. So the solution was to put the HDD in the Caddy in the SSD in the Hard Drive slot. Problem solved, I thought.

But of course, I completely forgot about it when setting up the Fusion Drive. And now, I have the very same symptoms: it is a CoreStorage LVG, but not a Fusion Drive.

My diskutil cs list looks the same as yours. Usually there should be a mention of Fusion Drive, but not for me.

Answer 2

It seems that the order of the disks is important, when you are adding a SSD after a HDD, the Fusion Drive is not functioning as it should be.

Look at this question: Is there a way to change order of physical disks in Corestorage