Archived posting to the Leica Users Group, 2008/08/23

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Subject: [Leica] RAID controllers?
From: hartzell at (George Hartzell)
Date: Sat Aug 23 17:34:50 2008
References: <>

Nathan Wajsman writes:
 > This whole thread has been quite interesting, as I have considered a
 > neater approach to external disks than the JBOD approach I use now.
 > So, going back to basics. I understand what Raid 0, 1, 5 mean. What I
 > would like is a Raid 1 or 5 solution with as much capacity as
 > possible, at a reasonable price, and able to work with my iMac (in
 > other words, no possibility for a Raid controller card, it must be
 > able to plug into one of the FW or USB ports and be controlled by
 > software). Does such a thing exist, or am I better off staying with
 > JBOD?

A simple solution would be to build a software RAID 1 (mirror) using a
pair of externally connected drives.  You can just use the software
that's included in OS X.  Being up to date (10.5) is probably a good
idea, I think that they've improved the software RAID over the

I think that firewire drives still have a slight performance edge over
USB drives, but the idea would work with either (or even, gasp, a
mix).  You can even experiment with the idea using a couple of usb
flash drives and learn what happens when one of the drives goes
missing, etc.....  In fact, I just did.

Gary will get a chuckle out of the fact that I don't think that you
should boot your OS on the raid if you do it this way :)....

You should be able to start Disk Utility (in Applications/Utilities),
and then in the big window select the RAID tab.

Drag the firewire devices (or the usb disks, or the flash drives) into
the window it calls the "list below", and make sure that the RAID type
is Mirrored RAID Set.  You probably want a Volume Format of Mac OS
Extended (journaled).

I was curious how it would handle the fact that you can't really plug
in both devices at exactly the same time.  A bit of experimentation
with some flash drives suggests that after it sees the first half of
the mirror it waits for a bit (a minute?) to see if the second half
will show up, and if so it brings it up intact, otherwise it brings it
up "degraded" using the first half that it sees.

I just goofed around with it a bit, and I ended up having to use the
diskutil command line rebuild discussed here:

after I intentionally messed up the raid.  Came back just fine

As I've said before, play with it before you trust it.  I don't know
what the performance implications of doing multiple devices over the
firewire bus will be, but the OS should be able to keep a writes going
to both devices in parallel pretty well....

I can also vouch for the readynas product.  I have an NV+ and have
heard good things about the newer devices.  Performance won't be
nearly as good but you can get much bigger w/ less futzing about. (their "mac corner").


In reply to: Message from photo at (Nathan Wajsman) ([Leica] RAID controllers?)