Being a fairly humble Mac consultant, most of my work is for self-employed folks with 1 or 2 machines. I’m always on them about data safety and backing up… (It’s good enough if I can get them on a single backup drive with Retrospect. I’ve also seen it where my clients have TURNED-OFF! the Retrospect backup scripts (rather than rescheduling or adjusting the script) because they popped up during their workflow.) A mirrored RAID (Redundant Array of Independent Disks) seemed like a good, no-brainer safety net for some of these clients. I’d never done a RAID before, so I decided to explore the situation.
RAID had always seemed like something suited more for a bigger enterprise situation, so had never considered it for these smaller system layouts. But I’ve gotten pretty paranoid about protecting my data in my home office, having had a single backup drive go belly-up on me before at a critical moment. Seeing how Apple had included a RAID feature in DiskUtility, I thought this must be meant for use on any OS X system. Upon exploration, I discovered the first basic distinction of hardware-based RAIDs and software-based RAIDs. The hardware-based setups of course being more robust but pricier, software RAID was the option I put my attention on.
Currently, the only software RAID options for Mac OS X seem to be SoftRAID or AnubisRAID by Charismac, and Apple’s DiskUtility RAID. While highly impressed with the softRAID demo, I went ahead with the Apple RAID Mirror because,well, it’s free. However, I found precious little information in the local help, nor on Apple’s support site, In fact, I was rather shocked at the lack of info out there regarding software RAID solutions for Mac OS X desktop (not Server). This quote from Annamarie Baldessari sums it up: “If you use Apple’s software RAID on your non-Xserve Mac you’ll be entrusting your data to an application that has no documentation and no support.”
The short of the story is, after running an initial setup where there was a syncronization failure, I found a more stable arrangement and I’ve been going along for about 6 months without any problems. Here’s how I got there:
My main machine is a Powerbook G4, so external drives were the only option. Economics ruling out a fancy hot-swappoing RAID drive-bay setup, I got a set of identical LaCie 250GB FireWire drives.
My powerbook has only a single built-in firewire port. Generally, I’ve sucessfully managed my FW devices by daisy-chaining them all together. I initially did this with the 2 LaCie drives, and that’s when I had the sync failure. Thinking that it might be better for the RAIDed drives to be equi-distant on the bus from the computer, I got a Belkin 6-port powered FW Hub, with each drive plugged directly into the hub, which is then plugged into my Powerbook. I always make sure the drives are powered up before I connect the data cable to the computer. As I said, all has been well for nearly 6 months.
I’ve considered getting a PC-Card FW adapter, to bring the bus even closer to home. That would probably be a better way for a powerbook to connect to the drives; but so far this has been working, and it’s the only way to RAID for an iBook or 12″ PB.
It IS a bit creepy that Apple provides no support for their product, so at some point I would rather go with SoftRAID, and that’s my recommendation to you. It is incredibly feature-rich compared to the Apple option.
The really nice thing about a mirror RAID is the peace of mind: if one drive goes down, or even if they get out of sync, you’ve still got your data, and it’s accessible.
A few relevant links:
- http://www.macintouch.com/raid.html
- http://www.macintouch.com/raid02.html
- http://www.acnc.com/04_01_00.html
- http://weblog.delacour.net/archives/2005/01/mac_os_x_power_tools.php
- SoftRAID 3 vs. Apple’s RAID and Apple Disk Utility
- Anubis RAID for Mac OS X
- http://www.backupbook.com/90Backup_Tips/0.default.html
- Homemade RAID
- http://ls.berkeley.edu/mail/magnet/2004/0290.html
Stepping up from software-only RAID, the superb WeibeTech offers Mac-friendly hardware systems:
- WiebeTech Microstorage Solutions, see the RAID link
Holistic Macintosh 
Gaia9 Said:
on April 5, 2006 at 3:07 pm
So, my RAID broke the other night, or rather, I discovered that it had degraded. Everything seemed to be going along fine, but I decided I wanted to take down the RAID because I wanted the full 500GB provided by my two 250GB LaCies. The GUI DiskUtility in OSX initially never showed a problem. It showed the two physical drives, grayed out since they were both configured into the RAID, then the Mirror RAID Virtual disk, with the RAID volume on it. Fine.
Since I wanted to break the RAID anyhow, I wanted to do it right so I could be sure the data all was safe on one drive while I reformatted the other one. I knew there wre more options available in the command-line diskutil, so I opened a Terminal window and first ran
diskutil checkRAID
It returned with "degraded", but wouldn't tell me which disk was out of sync.
The GUI DiskUtility now started showing the RAID as degraded, with only one disk configured; the other showed up as an available, unmounted disk with no partitions. I tried a few different approaches to see what was going on – separately mounting and unmounting the disks, powering them on independently. I isolated the one that had dropped out of the RAID, which when it powered up, the Finder said "unrecognizable disk…".
A RAID mirror is not a backup!!! It is redundancy against drive failure.