arup’s blog

When I first began my scsi experiments I had no idea about RAID and it was enough to find a decent bootable scsi controller card. My plan was to have my operating system and applications on the bootable scsi volume and main data on another drive. I was after speed and performance, but also a fun challenge.

The first card I tried, the Adaptec AHA-2940U2W did the job from the word go. I found a nice quiet drive in the form of a Seagate Cheetah 10K7 73GB 68-pin jobbie but wanted more speed. It all worked fine, but only marginally faster than my previous IDE set-up. I tried various cards from both Adaptec and Atto. And tried many workarounds such as Open Firmware, Firmware flashing, changing card slots and upgrading drivers. Now and again the system would boot but would then hang.

I gave up on the whole thing but continued to use my original Adaptec card. One day I was fired up again to start looking. Many hours reading forums and articles led me to think about the Adaptec 39160, but the Mac version. I had tried this card before, but it seemed obvious that I hadn’t tried the Mac version. So a few searches on ebay turned up a good priced one and when it arrived I wasn’t holding my breath. But it worked first time. My mouth fell open and stayed open for a while.

Was it faster? A bit, but not much. Bugger. More research led me to believe that it could be the cable that was slowing it down. So I bought a proper U160 cable. Speed increase, but still not satisfied. What next? Enter RAID.

What is RAID?

I can’t even begin to explain RAID as I only know the fundamentals myself. But the term means Redundant Array of Inexpensive Disks. Basically making one large volume from lots of small cheap disks. The minimum is two of course. For speed and performance there was RAID 0 or Striped RAID. The data is split across two or more physical drives to create one volume. Reading and writing to the volume is faster than a single drive due there being more spindles. But if one of those drives fail then the whole volume fails.

RAID can be set up using software or hardware methods. Mac OS X has RAID software built into it using Disk Utility so it’s very easy to create a RAID set merely by dragging and dropping disks into the window and selecting the type of RAID that you want - mirrored or striped.

How I did it

Finally a chance to reach the level of performance that I was after. All I would need was a second identical Seagate Cheetah U320 10K7 drive just like the one that I had. Off to ebay again. This was my plan.

• Tidy up my current boot drive clone it onto the back up drive
• Test the clone by booting from it
• Boot from another bootable drive and create the striped RAID array
• Clone the back up drive onto the new RAID volume
• Boot from the RAID volume

The tidying up involved deleting any large redundant files and then giving it the Disk Warrior treatment. Then I had to test the clone because my original boot drive was about to be wiped when it became part of the array. The drive where my files live is also bootable so I booted from there to use Disk Utility to create the array. This was the easiest part. Then copying the back-up onto the newly created RAID volume using Carbon Copy Cloner which I used to create the clone in the first place.

System Preferences > Startup Disk > Mac OS X, 10.4.11 on Boot RAID. Eh Voila!

Is it fast? You bet.

Share This

This entry was posted on Tuesday, January 15th, 2008 at 11:30 am and is filed under achievements, ongoing learning. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.