WARNING

This information is provided with no warranty of any kind-- USE AT YOUR OWN RISK.

Summary

You need to use flash-cache and that requires Oracle Unbreakable Linux 5.5 or newer.  Dell's FUSIONIO solid-state-disk devices (the IO and IODUO) are "unsupported" by DELL with Unbreakable Linux.

HOWTO

Here's how we got it to work on a DELL R910 with DUAL SAS drives (to store the OS and Database Software) and a FUSION-IO Duo 640GB Drive which will hold the database

1.  Install Oracle Unbreakable Linux 5 update 5.  You can download it from Oracle Directly for testing and pay for licensing when you need to.
2. If you are not part of the ULN you need to remove up2date with "yum remove up2date"
3. then you need to configure your yum repositories (note that the destination name is "ol" for "Oracle Linux" rather than "el" for "RH Enterprise Linux"):

   1. # wget http://public-yum.oracle.com/public-yum-el5.repo
      # cp public-yum-el5.repo /etc/yum.repos.d/ol5.repo

   2. then edit the ol5.repo file and
      
      1. make sure the el5_ga_base is enabled
      2. make sure the el5_u5_base is enabled
      3. make sure ol5_u6_base is enabled
      4. make sure everything else is not enabled
4. then you need to update your system with "yum update" (in our case it was over 248 patches)
5. Once that's done now you need to install gcc and a number of other libraries such as "lm_sensors" and the relevant development kits because you'll need it to rebuild the fusion IO driver for your specific kernel.
6. reboot
7. nowdownload the FusionIO drivers for RedHat Enterprise Linux 5 from http://dell.fusionio.com into an otherwise empty working directory
8. now follow the directions in the PDF provided by http://dell.fusionio.com
9. Once you have the fusionio rpm's installed you should be able to see your FusionIO card whether or not you have the driver loaded with the "fio-status" command

We have successfully repeated this process on numerous systems without failure.

Contact us if you have any questions or need help, we've been working with *NIX for >25 years and have done all manner of development and driver work.