Software RAID with external drives

February 26, 2006 9:23 PM

Experiences with software raid with external USB drives? XP and/or OSX? Ever have problems with the drives spinning down when not in use and the raid set breaking in the process? Does this shorten the life of the drives in any as compared to mounting internal of a case using IDE or SATA?
posted by joshgray to technology (5 comments total)

Don't do software RAID. Ever. Especially don't do it if you're running external drives. Just run incremental backup software like SyncBackSE by 2BrightSparks.
posted by creeront at 10:28 PM on February 26, 2006

Software RAID is quite fine, provided you can trust the software behind it. Are you doing RAID1 I hope?

If the disks are spinning down, perhaps your OS is the culprit? It certainly shouldn't ever break software raid volumes; the disks are supposed to spin back up when they are accessed.

I haven't seen anything to indicate drives in a USB enclosure will last less long than inside your PC; usually the OS is what tells them to spin down, and it applies to internal disks as well as anything in a usb/firewire enclosure.
posted by AaronRaphael at 11:23 PM on February 26, 2006

I agree with AaronRaphael. There shouldn't be any problem at all. The OS doesn't really care about what the interface to the device is, the software interface to the device is always the same.

Software RAID is often the way to go in situations where you're not terribly concerned about performance. There's less worry about hardware compatibility.
posted by joegester at 3:24 AM on February 27, 2006

Most of the USB enclosures I've seen, in an attempt to be quiet, don't cool as well as they should. So the drive runs hot, and hot drives fail sooner.

You might need to run some kind of utility on the drives to prevent auto-spindown... but keep in mind, that may make the heat problem worse.

If you get well-cooled drives with spindown disabled, it should work fine. But keep in mind that this is usually pretty noisy, because small fans have to be loud/whiny to move much air.
posted by Malor at 4:28 AM on February 27, 2006

External drives are slow, unless they are SATA.

Windows 2000/XP/2003 all prevent you from "upgrading" external USB/Firewire drives from Basic to Dynamic. The Windows disk admin tool post-NT4 will only let you software RAID ("mirror" or "stripe") dynamic disks.

To get around this you can set a Registry entry to be true:
EnableDynamicConversionFor1394

HOW TO: Convert an IEEE 1394 Disk Drive to a Dynamic Disk Drive in Windows XP

Software RAID is a common topic on Ask.

I run hardware RAID-5 on my main server. I also use software RAID-1 for a non-critical web server. It's recovered a few times using one of the mirror drives. I use software RAID-0 for a huge near-line 1.5TBG backup box. I use several software RAID-1s for network storage of video files. They work okay.

One thing with Windows is that it is sensitive to the chaining order of external firewire devices for the striping. SO if you do do this, make sure you label the cables and their sequence. Otherwise, if youchange configuration, you may find that Windowsw refuses to mount the drives again unless you go into diskpart.
posted by meehawl at 5:00 AM on February 27, 2006