The LSI Logic MegaRAID Card
2. 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
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
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.
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An excellent article. I have been trying to setup something like this. I just went thru 2 weeks of trying to get software raid 5 to work in Ubuntu. I searched the net for how-to or step by step instructions and could only find bits and pieces. Nothing worked. Linux users need to remember that us wanna bees don't know even the slightest of commands! In every article I found, they assumed you knew "some" basic commands. I tried reading and learning, but I couldn't find a good learner for linux. Anyway, having decided to do a hardware raid 5 with Ubuntu desktop seemed like my only hope. Then I find this article here, and it is exactly the way EVERY article should be done, step by step, assuming the reader knows nothing. This article is VERY good and thorough! Congratulations Benjamin Webb, you did a great job! -Blueuniform
interesting article, but the beauty of linux software RAID5 is that an array rebuild will happen automatically when you replace the faulty drive (well you have to tell it that you replaced the drive using mdadm). you can even simulate a failure and then watch it rebuild the array to get an idea of how your system will respond under different scenarios. here's a snippet of what needs to be done to replace the missing drive/partition:
Rebuilding:
To remove the failed partition and add the new parition:
mdadm /dev/mdX -r /dev/sdYZ -a /dev/sdYZ
where X is the array number (0,1,etc) and YZ is your disk/partition (sda3 for example)
e.g.:
mdadm /dev/md0 -r /dev/sde3 -a /dev/sdr3
(where sde3 is the 3rd partition on your faulty drive, and sdr3 is the 3rd partition on the new drive)
Watch the automatic reconstruction run with:
watch -n1 cat /proc/mdstat
I understand that people fear the console commands. It can be a bit scary at first. But mdadm is pretty simple when you're used to console apps and a little bit of linux. It's mostly just mdadm and such. I currently run two software raids with 7 and 5 disks.
i believe his concerns with software raid5 were not just the rebuilding points. i believe he liked the fact that if the os drive took a crap, he could take the card and array and move it to any operating computer and it would power up and work. if you lose the operating system that wrote the software raid array, you have lost the array.