Promise Pegasus R6 & Mac Thunderbolt Review
by Anand Lal Shimpi on July 8, 2011 2:01 AM ESTTarget Disk Mode
Another use of Thunderbolt is Target Disk Mode. Connect any two 2011 iMacs, 2011 MacBook Pros or any combination of the two with a Thunderbolt cable, reboot one of them while holding down the T key and you'll boot into target disk mode.
Hold down T and you'll get both Thunderbolt and FireWire logos at boot
With only Thunderbolt connected, the FireWire logo disappears - you're now in Target Disk Mode over TB
In this mode the target Mac boots into a special EFI state that allows all of its drives (HDDs, SSDs, optical, anything connected to the computer) to be mounted by the host Mac. The drives appear like normal removable disks on the host Mac:
MacBook Pro accessing the iMac's sole HDD over Thunderbolt in Target Disk Mode
You even have to eject them all manually before turning off the target Mac.
Don't get too excited though, since the target Mac isn't running full blown OS X it only implements basic storage drivers and optimizations. As a result, peak performance is no where near what Thunderbolt is capable of. Regardless of whether I put the 15-inch MacBook Pro or 27-inch iMac in target disk mode, I never saw more than 61MB/s from the target.
Performance was erratic as well. Sometimes I'd see transfer rates drop all the way down to 9MB/s before jumping up to 30MB/s and then 60MB/s. On average I'd say I saw transfers around 40MB/s.
The functionality is great, however I believe target disk mode would be a killer feature of Thunderbolt if it could operate at peak performance. In its current implementation, it's faster than a WiFi transfer but a bit slower than a good Gigabit Ethernet network transfer. If we could get line speed transfers, being able to move data between two modern Macs at multiple Gbps would be great.
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PrincessNybor - Tuesday, July 12, 2011 - link
I'm actually looking forward to using Target Display Mode when I pick up my new 27" iMac this month (just holding out for Lion). My work computer is a 15" MacBook Pro with Thunderbolt, and while the display is good for a portable, I'd love access to a 27" display! Some of the applications I work with won't be installed on the iMac, since that will be a personal desktop and not a work machine. This is a good solution for others in my situation.osteopathic1 - Thursday, July 14, 2011 - link
I just plugged in my old 23" Cinema Display DVI into a $6 minidisplay port/DVI adapter and it worked like a charm.onebear - Saturday, September 24, 2011 - link
Please see this discussions from Apple Support forum.https://discussions.apple.com/thread/3181015
It is not working with iMac 2011. And having many unsolve issues.
nanofunk.net - Saturday, January 7, 2012 - link
there are lots of known problems and promise won't answer or react on any of them.see a roundup of problems here:
http://www.nanofunk.net/caution-with-promise-pegas...
also there are other issues as reported in the apple forums:
https://discussions.apple.com/thread/3181015?start...
the only thing we can currently do is to boycott promise until the give an official statement and release a bugfix to support larger HDDs and address the issues/bugs (drive-ejecting bugs, etc.)
Rdubs - Friday, April 20, 2012 - link
Anyone know if I can throw in 4x 4tb 3rd party drives into a R4?What's the limit? Can't find a list of what mfg' s hard drives play well
with R4.
Many thanks
frabber - Thursday, October 25, 2012 - link
anybody know whether this is possible? with some kind of thunderbolt enabled motherboard?odedia - Monday, April 14, 2014 - link
WD RED 4TB drives are pretty affordable now, for the price of the 8Tb R4, I can get a diskless R4 and 4 red drives, resulting in 16tb total. They question is, would the RED drives match the performance of the R4? They are 5400 rpm drives, though quite reliable (much better than a green drive).badex - Thursday, December 31, 2015 - link
Hi,Have had my pegasus R4 for a couple of years. its been effective but i think i'd like to take a step up to using SSD drives. what SSD drives would you recommend for the pegasus R4?
thanks