Typically multi-bay external storage devices tend to utilize 3.5" drives due to the lower cost and higher capacities. The downside, however, is that 3.5" drives are physically larger and heavier, which makes a multi-bay enclosure rather difficult to move around on a regular basis. To fix this, Promise is offering a 4-bay 2.5" RAID solution called the M4.

Promise Pegasus2 Lineup
  M4 R4 R6 R8
Form Factor 4 x 2.5" 4 x 3.5" 6 x 3.5" 8 x 3.5"
Supported RAID Levels 0, 1, 5, 6, 10 0, 1, 5, 6, 10 0, 1, 5, 6, 10, 50 0, 1, 5, 6, 10, 50, 60
Connectivity 2x Thunderbolt 2 (20Gbps each)
Available Capacities 4TB 8TB 12TB & 18TB 24TB & 32TB
DImensions (HxWxL) 4.2" x 5.0" x 6.6" 7.5" x 9.6" x 7.3" 9.8" x 9.6" x 7.3" 12.2" x 9.6" x 7.3"
Weight 5.5lb / 2.9kg 15lb / 6.8kg 20.1lb / 9.1kg 24.2lb / 11kg

Aside from capacity, the M4 offers everything that the R4 does as you get hardware RAID 5 and two Thunderbolt 2 ports for daisy-chaining. The weight comes in at almost one third of the R4's weight and the dimensions are considerably smaller too, which makes the M4 a lot more portable than the rest of the Pegasus2 lineup. Sadly Thunderbolt 2's ten watts of power is not capable of powering the M4, so it is not a fully portable solution like regular external hard drives are.

The M4 is available for $999 in the Apple Online Store and the target market for the M4 and the whole Pegasus2 family is video professionals. Promise markets the M4 as a solution that offers portability for over an hour of uncompressed 4K footage. While there are arguably cheaper and larger external 3.5" hard drives around, the M4 provides redundancy via RAID 5, 6 and 10, which is more or less a must for professional video editing because data loss could end up being very expensive.

Our review unit shipped with four 1TB 5,400rpm Toshiba hard drives. These are 9.5mm i.e. two-platter drives, so we are not dealing with super high density here. Promise told us that they are not offering 4x1.5TB or 4x2TB configurations due to price sensitivity as $999 is quite expensive to begin with, although I am not sure if I agree because I could see video professionals paying more for increased capacity. In the end, 4TB is not that much if you deal with 4K video.

Fortunately Promise has made hard drive swaps convenient as pressing the button on the bay will free the lever, which you simply pull to get the drive out. The drives are attached to the bays by four standard hard drive screws, so any 2.5" drive will work. Officially Promise only guarantees compatibility with the Toshiba drive, although the user manual suggests that the drive does not have to be the same make and model.

Getting inside the M4 is fairly easy. There are a few screws that need to be removed until the top comes off and you end up having access to the PCB along with the rest of the components (PSU, fan, etc.). The RAID controller is covered by the heat sink, so I do not have a photo of it, but I was told that the silicon itself is from PMC with custom Promise firmware. A quick look at PMC's RAID controller lineup suggests that the silicon is the PM8011 SRC 8x6G, which is an 8-port SATA/SAS 6Gbps controller with a PCIe 2.0 x8 interface. 

Like many Thunderbolt devices, the M4 has two Thunderbolt 2 ports for daisy-chaining. The Thunderbolt controller is Intel's DSL5520 with two Thunderbolt 2 ports (i.e. four channels) and it connects to the RAID controller through a PCIe 2.0 x4 interface. Intel lists the bulk price as $9.95 on their ARK site and the TDP is 2.8W.

Test Setup

Unfortunately I do not have a Mac with Thunderbolt, so the results and analysis are limited to a Windows based system. Based on what we have talked with manufacturers, there is some difference in performance between Thunderbolt in Windows and OS X. A part of that comes from the fact that in PCs, the Thunderbolt controller is connected to the PCIe lanes from the PCH, whereas in Macs they come directly from the CPU. The Windows drivers are also not as good as the native OS X drivers, which I guess is not a surprise given that Apple has always been the biggest supporter of Thunderbolt. Either way, the results should represent performance under both OSs as long as we are not close to saturating the interface.

CPU Intel Core i7-4770K running at 3.3GHz (Turbo & EIST enabled, C-states disabled)
Motherboard ASUS Z87 Deluxe (BIOS 1707)
Chipset Intel Z87
Chipset Drivers Intel 9.4.0.1026 + Intel RST 12.9
Thunderbolt Adapter ASUS ThunderboltEX II/DUAL
Thunderbolt Drivers 1.5.1.1
Memory Corsair Vengeance DDR3-1866 2x8GB (9-10-9-27 2T)
Graphics Intel HD Graphics 4600
Graphics Drivers 15.33.8.64.3345
Desktop Resolution 1920 x 1080
OS Windows 7 x64
The Pegasus2 M4: Software
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  • Kristian Vättö - Sunday, September 14, 2014 - link

    I hope you understand that there is no central AnandTech office with every possible gadget and tool at our disposal. I don't have any other Thunderbolt enclosures since this was my first TB review, so I wouldn't have anything to compare the M4 to. Anand used to run our Thunderbolt coverage since he had the best tools for that, and it will take some time before we get everything migrated. Reply
  • melgross - Sunday, September 14, 2014 - link

    You couldn't get the site to cough up $40? Or use your smartphone. There are plenty of apps that measure sound levels. I can't speak to the accuracy of Android apps because there are so many phone models out there that they may not all be calibrated. But the ones for the iPhone, such as Audio Tools, also available for Android, is. Mine measures within 1db of my lab meter. Reply
  • melgross - Sunday, September 14, 2014 - link

    I forgot to mention that using an app such as Audio Tools is better because you can also use the very accurate spectrum analyse tool. This is important for useful noise testing because all noise is not equal. Low frequency noise doesn't sound as loud to us as mid frequencies and higher frequencies do. This shows a live reading chart. Also great for detecting hum, and other spikey noises. You can also save the chart and put into the review. Reply
  • bigboxes - Monday, September 15, 2014 - link

    I don't comment on everything. However, Anand is gone. You've got to stop using him as an excuse as to why you don't do someting. Move on. It's almost painful reading your comments. Yes, Anand is gone. Now, it's time for you to move on. Reply
  • melgross - Sunday, September 14, 2014 - link

    Is like them to spend $40 and buy a meter which is accurate to within a couple of dbx such as the Radio Shack model. At least we would get some idea of how loud it is. It doesn't need to be exact. Reply
  • Kristian Vättö - Sunday, September 14, 2014 - link

    I definitely want to test with a Mac because obviously that is the target market of Thunderbolt products. Unfortunately I don't have one at my disposal and since I have to spend my own money on it, I want to make sure that what I buy is worth it in my opinion (I currently have a 2010 MBA, but it's still serving me fine so I haven't seen a need to upgrade yet). Reply
  • colinstu - Saturday, September 13, 2014 - link

    I'd love to see four WD1000CHTZ thrown in this puppy and see how it compares. (10k RPM, SATA 1TB drives). They're 9.5mm too just like the ones used here. Or take a WD1000DHTZ and take the 2.5->3.5 "icepack" off. Reply
  • jseliger2 - Sunday, September 14, 2014 - link

    <i>While there are arguably cheaper and larger external 3.5" hard drives around</i>

    There was just a thread about this issue over at Ars Technica: http://arstechnica.com/civis/viewtopic.php?f=19&am... , and I"m curious about what those other external drive bays might be. Arsians list an OWC option, a Western Digital version, and a Drobo version. They're all costly. Are there other alternatives?
    Reply
  • Kristian Vättö - Sunday, September 14, 2014 - link

    I meant external HDDs in general, including USB 3.0 ones. If you are just looking for a single drive, then USB 3.0 is fine because a 3.5" HDD cannot saturate the USB 3.0 interface anyway. It's only when you start doing RAID (or SSDs) that Thunderbolt becomes beneficial. Reply
  • jseliger2 - Sunday, September 14, 2014 - link

    I meant external HDDs in general

    Oh—I see.

    I'm still curious about the multi-bay enclosure space, since those multi-bay enclosures still seem to be shockingly expensive. Perhaps that will remain true: http://www.anandtech.com/show/8529/idf-2014-where-... , but I'd like it not to be. As they say in that Ars thread, the four-bay Thunderbolt Drobos are about twice the price of the equivalent USB 3 model.
    Reply

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