Build a Cheap and Fast RAID 5 NAS

The LSI Logic MegaRAID Card

The LSI Logic MegaRAID adapters are ROM-based. So the usage model is to boot the computer and then start the controller's software with a control-key sequence. The controller's software is a BIOS-style menu-driven interface that allows you to set up, upgrade, or repair your RAID 5 array. When your computer boots up, you will see the LSI Logic adapter's control instructions flash on your monitor, as shown in Figure 1.

Figure 1: Splash screen

When you press <Ctrl>+M in response, the LSI Logic MegaRAID will start its software from ROM to allow you to manage your RAID 5 array. Figure 2 shows the main menu of the MegaRAID software.

Figure 2: MegaRAID main menu

Figure 3 shows how menus pop up in the MegaRAID software.

Figure 3: MegaRAID menu pop-ups

Note that in Figure 3 I have moved the cursor to "Configure" and then pressed the <Enter> key, to pop up the "Configure" menu. I then moved the cursor to "New Configuration" to initialize the RAID 5 array of drives. The MegaRAID software has then popped open a third menu that says "Proceed?". To finish configuring a new array I would then move the cursor to "YES" and hit <Enter>. While the interface is a flashback to the days of MS-DOS, it is functional and reliable.

The MegaRAID cards allow what I call the "sane" RAID 5 repair procedure:

Step 0: Hear the shrill wailing of the MegaRAID card
Step 1: Identify which hard drive has failed
Step 2: Shut down the RAID NAS
Step 3: Remove the failed hard drive
Step 4: Get in your car
Step 5: Drive to your local computer retailer and buy a replacement hard drive
Step 6: Return home
Step 7: Install the new hard drive
Step 8: Kick off the RAID controller's recovery procedure
Step 9: When the recovery is complete, reboot the server and carry on

I named this the "sane" procedure after looking at software RAID and concluding that recovering a drive under software RAID was (for me) insane.