Many people complain that SATA II RAID works slower than SCSI RAID, however the only reason is misconfiguration. When configured properly, SATA II can overtake SCSI RAID.  In this article I will go through 3Ware / AMCC 9550SX configuration. There are several pitfalls to avoid while configuring this card.

3Ware / AMCC 9550SX is natively detected by FreeBSD. 3Ware / AMCC also gives out drivers for this controller. One can download them and open to /usr/src/sys/dev/twa directory and recompile the kernel or compile a module and use the module instead.

9550SX also gets new firmwares quite frequently. These can easily be installed using the tw_cli utility. A very good example exists in the manual of tw_cli utility.

Now, some things to be careful about. First of all, most SATA II drives come with jumpers installed which limit them to SATA I compatibility mode. Many people who make these systems do not know this fact. I have myself heard from the hardware builders that the drives support native sata II and there shouldnt be a problem and they were wrong. So only trust yourself. It is easy to check this using the tw_cli utility(or the web interface, see below) using the '/c0/p0 show all' command (for first drive) you should be seeing:

/c0/p0 SATA Link Speed Supported = 1.5 Gb/s and 3.0 Gb/s
/c0/p0 SATA Link Speed = 3.0 Gb/s

If you do not see 3.0 Gb/s then you have the jumper on and your drives work with half interface speed!

Now we should check if the write caching and NCQ enabled on the controller itself. For write caching, you really should have a BBU (Battery Backup Unit), otherwise you might loose a lot of data if a power failure occur. For seeing this information you should issue '/c0/u0 show all' command. In the output, you should be seeing,

/c0/u0 Cache State = on
/c0/u0 Command Queuing Policy = on

If you are seeing that these are not enabled, you can enable them by issuing these commands. '/c0/u0 set cache=on' and '/c0/u0 set qpolicy=on'

One can also install the 3dm utility for managing the controller from web. To install it just do:

#cd /usr/ports/sysutils/3dm/
#make install && make clean

Then enter twdm2_enable="YES" to /etc/rc.conf and run '/usr/local/etc/rc.d/3dm2 start'

Then just go to https://YourserversIP:888/ URL, the default password is '3ware' because of the obvious reason, you should change it :)

Some arrays also must be initiliazed. If you are using less than 5 disks then usually this is not required. However when you do a verify operation, the array would be initialized automatically.

Some other settings which can be done easily from the web interface is to set the background task rate from controller settings. Normally you can set the verify rate to 'faster I/O' this means that verify operation will pause when there is high I/O load and start again when the load goes down.

You can also set Auto Verify, Queuing and Write Cache easier than using the tw_cli utility. By clicking on drive information from information menu you can get to see the drive statuses etc. By clicking on the port number you can see the drive speeds. You can use the web interface as an alternative to using the tw_cli to see the drive interface speeds etc.

After all these settings, you should be seeing amazing speeds. :)