SoftRAID 3 OverviewBy: Scott Doenges - Revised: 2007-01-24 richard
IntroductionSoftRAID 3 is a backup solution that takes a users existing hard disks and groups them together to give them more speed, capacity and/or instantaneous backup. With it, users do not need a hardware solution to get RAID (Redundant Array of Independent Disks) protection.
Scott will discuss the features and benefits of using SoftRAID 3 to mirror volumes, as an alternative to Apple RAID.
What is SoftRAID 3?
SoftRAID 3 is a piece of Mac OS X software that builds software RAIDs (Redundant Array of Independent Disks). It includes an application and disk driver that allows you to take our existing hard disks and group them together to give you more speed, capacity and/or instantaneous backup. It gives you RAID for your existing disks without the need for any other supplemental hardware and many additional benefits of other RAID software like Apple RAID.
SoftRAID 3 is capable of creating non-RAID, RAID 0 (stripe) and RAID 1 (mirror) volumes. It works with five types of hard drives or disks: FireWire, USB, SCSI, ATA and Fibre Channel, and it supports creating RAIDs on combinations of those drives (so you can set up a RAID between an ATA and FireWire disk, etc).
A recent update allowed the ability to have a SoftRAID-mirrored startup volume, a very nice feature that was missing from the first release.
It's important to note that SoftRAIDs will only be as fast as your slowest drive - so if you have a 7200 RPM FireWire 800 drive mirrored with a 5400 RPM FireWire 400 drive, your RAID's maximum speed will be 5400 RPM and 400 Mbps.
Different RAID types that SoftRAID can create
SoftRAID 3 has a nice GUI with physical disks shown on the left and volumes shown on the right, with red pipes illustrating which disks belong to which volumes and vice versa:
Working with RAIDs is easy, especially since SoftRAID does not require you to reformat a disk to create a RAID volume (which Apple's RAID does require). Select the disks you want to create a mirror of, and use the "Convert" menu to turn them into SoftRAID volumes. You can then create a new RAID volume with the simple GUI shown below:
You can also easily add and remove disks to and from a RAID. If you decide you want to use one of the disks in a mirror as an independent disk, you can split it off of the RAID and create a separate volume from it, without having to reformat.
If one of the disks in your RAID ever gets out of sync, SoftRAID's background monitor will display a warning that you need to open SoftRAID and let it rebuild your RAID (i.e. make sure all disks in a RAID contain identical data). SoftRAID can also rebuild your RAID in the background while you continue to work. Rebuilding can be pretty slow - it took a G4/400 about 4 hours to rebuild a 75 GB RAID volume I set up on two ATA disks.
On the other hand, if you have RAID sync problems with Apple's RAID, you would not receive any kind of notification - you would only find out if you happened to open Disk Utility and check the RAID status. This does not apply to Apple's Xserve or Xserve RAID, which can email notifications and alerts.
You could also use the command line utility diskutil to check status of raid devices: "diskutil checkRAID
". This will output the RAID status, and could be used with cron to routinely check your RAID status, and even set up scripts to send out email when Apple RAID has issues.
One of the main drawbacks of using SoftRAID is that your existing bootable CDs/DVDs you use for installation/troubleshooting will not be able to recognize SoftRAID disks since the driver is not present in the CD's System folder.
Thankfully SoftRAID realizes this and gives you a solution - under the Utilities menu you can create SoftRAID startup CDs, or modify an existing boot CD/DVD (i.e. a Mac OS X Installer disk, or your DiskWarrior/TechTool boot CDs). You just insert your source disk and SoftRAID creates a temporary disk image of your CD, which it then installs the SoftRAID disk driver onto. It then asks for a blank CD and burns the modified image:
As a side note, I found another review of SoftRAID 3 (link dead) that states the SoftRAID engineers made sure that their disk driver would be fully compatible with DiskWarrior. This is a good sign that SoftRAID is aware that they need to work with other great Mac utilities. I ran DiskWarrior 3 on my SoftRAID volume from a modified boot CD, and it appeared to work fine.
Pros and ConsPros
So why should you buy this tool when Apple already gives you free RAID functionality with Disk Utility? The SoftRAID website has quite a list
of ways in which SoftRAID is better than Apple's RAID, but is it really worth it?
Here are a few of the more notable pros to using SoftRAID:
- Lets you easily create and modify RAIDs dynamically - add or remove disks at will.
- You don't have to reformat to convert to a SoftRAID volume.
- Lets you mix drive and bus type.
- Fast read speeds with mirror RAIDs.
- Much less expensive than a hardware RAID solution.
- Quickly converts Apple RAIDs and volumes to SoftRAID volumes.
- Has a background monitoring app that warns you when a RAID has errors - Apple gives you no warnings at all.
- Includes special I/O optimizations for different purposes (i.e. workstation, server, digital video, etc).
And here are a few reasons why you might not want to use SoftRAID:
- SoftRAID volumes will not appear on systems that don't have the driver installed (which means target disk mode would not work if the host system doesn't have the SoftRAID driver - you would have to run SoftRAID on the host system and let it install the driver).
- You must modify existing boot CDs to work with SoftRAID volumes.
- SoftRAID disk names don't appear in the "Bootpicker" (the startup disk interface you see when holding down Option at startup) - minor but annoying. This problem only affects drives that were originally Apple drives, that were converted to SoftRAID drives. I am told that this will be fixed in a future SoftRAID update (3.1.3).
- Should have email alerts when RAIDs are out of sync. I am told this feature is highly requested, so it will be available in a future update as well.
- I experienced two kernel panics while setting up RAIDs across different bus types (using a Weibetech FireWire to ATA bridge) - this may have just been a fluke.
- Probably more likely to have stability issues with Mac OS X (for example, after a major OS upgrade). This is just a theory! SoftRAID support assures me that in the event of problems caused by a major OS upgrade, the issue is resolved with a software update within 30 days.
We purchased SoftRAID 3 as soon as it was released without realizing it did not yet support bootable RAIDs, which is exactly what we bought it for. Now that it has this ability, it is much more useful to us and many others.
As I mentioned, I did experience two kernel panics (which I think were caused by me using two Weibetech ATA-FireWire bridge devices to create RAIDs). Once I switched to internal ATA and LaCie FireWire drives for my RAIDs, I did not have any stability issues.
I still think it is missing one or two nice little features (such as emailed RAID alerts), but overall this is a very simple yet useful tool for creating and managing RAIDs. The special I/O optimizations it can do may make it very attractive to video/audio pros wanting the best possible performance.
SoftRAID's benefits and ease of use far outweigh Apple's RAID. As long as you don't mind re-burning CDs to work with your SoftRAID volumes, I would definitely recommend this application.
- Mac OS X 10.2 or higher
- Built-in G3/G4/G5 processor (works with processor upgrades, but not supported)
- 2 or more drives for RAID
- Beige/B&W G3s not recommended for FireWire RAID
How much does it cost?
$129 for a downloadable copy and $149 for a physical copy.
SoftRAID 2.x is still available for Mac OS 9 users for the same price.