Download the driver RPMs from adaptec website, as I have 5805z controller, I downloaded the drivers from here :
http://www.adaptec.com/en-us/support/raid/sas_raid/sas-5805z
http://www.adaptec.com/en-us/downloads/rh/rhel_5/productid=sas-5805z&dn=adaptec+raid+5805z.html
You will get a file like this :
aacraid_linux_rpms_v1.1.7-28700.tgz
unpack it :
tar zxvf aacraid_linux_rpms_v1.1.7-28700.tgz
to get :
aacraid-1.1.7-28700.rpm
install rpm :
rpm -ivh --force aacraid-1.1.7-28700.rpm
it will only extract the files to /opt/Adaptec/aacraid :
cd /opt/Adaptec/aacraid
mkdir mods
mv aacraid_prebuilt.tgz mods
cd mods
tar zxvf aacraid_prebuilt.tgz
rm *.tgz
now you have prebuilt module for different kernels, copy the appropriate kernel module to aacraid.ko path, a command like :
cp aacraid-2.6.18-238.el5xen-x86_64 /lib/modules/2.6.18-274.18.1.el5xen/kernel/drivers/scsi/aacraid/aacraid.ko
if you have locate package installed, you can easy find all aacraid.ko files :
locate aacraid.ko | xargs -n1 modinfo | grep vers
when it is complete, reboot the server.