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How To Upgrade Promise Pegasus Thunderbolt RAID With New Drives

LATEST UPDATE – May 2021 – for original solutions scroll down…

I’ve offered the info below about which hard drives to upgrade your Pegasus R4 with for several years now, updating as things have changed, and it’s mostly still valid.

But just recently I had 2 HDD failures in my Pegasus within a month of each other, so I felt that a new 4-Bay RAID enclosure with dual Thunderbolt 3 would be the way to go – a fresh start for my RAID 5 solution.

And this is what I came up with… (fanfare…) the OWC 4-Bay Storage Enclosure with Dual Thunderbolt 3 Ports – it’s also known as the OWC ThunderBay 4.

OWC 4-Bay Storage Enclosure with Dual Thunderbolt 3 Ports

The OWC is sitting under my desk right now, with the 4 Toshiba 4Tb HDDs from the Pegasus R4 (two new, two a few years old) sitting in it. It’s pretty quiet and performance over Thunderbolt 3 is great (Up to 1527MB/s sustained) – I am very happy!

The enclosure can be purchased with drives or empty – and the latter option that I chose comes at a reasonable price and includes OWC’s RAID software, SoftRAID XT, RAID-5 Pre-configured if you choose included drives.

A word about the software – you receive a serial number on the enclosure, and for mine, that was for software v5. But… v5 doesn’t run on Mac OS Big Sur – for that you need v6. However, it comes with a 14 day free trial period, so there was time to contact OWC and receive a free upgrade serial number, no problem (Thanks OWC EU!)

The box includes a short Thunderbolt 3 cable – if yours will be under the desk you’ll need a longer cable; I discovered my 2m Apple USB-C charging cable from a MacBook Pro didn’t work, although the Thunderbolt 2 cable I was using with the Pegasus is fine (with an Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter)

So, I’m happy to recommend the OWC as the best solution I’ve found, for replacing an ageing Promise Pegasus R4.

Original article, 2016:

If, like me, you bought a Promise Pegasus R4 RAID with 4x 1tb or 2tb drives as soon as Thunderbolt was released and the Pegasus was available, you’ll probably have considered upgrading the unit with larger capacity hard drives, now that bigger drives are readily available.

Or you might have already upgraded, and now individual drives are failing and needing replacement – if so, read on…

I use my Pegasus R4  configured as RAID 5  for video editing – if one drive fails, the others have all the data and I can hot-swap that drive and move on relatively quickly.

So, for the upgrade, my first thought was – how can I maximize a Pegasus R4 that came with 4x 1tb drives? I’ve recently purchased Western Digital WD 6TB Drives for the Drobos we use as local USB backups, without problems, so thought these would be a good bet.

To be safe, I consulted the Promise website and found their list of recommended drives – they test for compatibility and only suggest the ones that go through that process.

But there weren’t any drives bigger than 4tb, and no mention of Western Digital. Promise had a Live Chat facility, and an agent responded immediately – but could not confirm if any drives larger than 4tb could work successfully with my Pegasus R4, as none had been tested.

The agent also confirmed another important couple of points when upgrading all of the drives in a RAID:

  • All drives should be the same capacity; if you put a 4tb drive in a RAID where the other drives are 2tb, that 4tb drive will only show up as 2tb
  • You do not have to install the identical make and model of physical drive, but they must of course be the same type (HDD or SSD), same interface – SATA 3 Gb/s or 6 Gb/s, and same spin speed : 7,200 RPM or 15,000 RPM
  • ideally all drives should be replaced at the same time (of course, you must back up the content elsewhere first, then add it back to the new array you will create)

Next, I sought the advice of colleagues on Creative Cow – the verdict was unanimous: Promise will have tested many drives so it really is best to use only the ones they recommend. Although this was a little disappointing, especially as the Promise-recommended drive I found on Amazon was more expensive per terabyte than the 5tb and 6tb drives I found, I decided to play safe and avoid the huge hassle of a RAID problem in the middle of a big edit.

In this case, the drive that Promise tested and recommend was the Toshiba 4TB 7200 rpm 3.5″ – internal hard drive – click to see if it’s available on Amazon in your country.

Toshiba Internal Hard Disk Drive

Update early 2021 : We’ve found the drive above to be unavailable in the UK, but the Toshiba X300 is available, usually at a good price, and meets the criteria required : 

Toshiba X300 4TB 7200RPM 128MB 3.5″ SATA

If you find it’s unavailable, read on for other upgrade options or back to the top for the OWC…

Toshiba X300 4TB 7200RPM 128MB 3.5" SATA
How to replace a single failed drive in Promise Pegasus R4:

– With the Pegasus still connected to power, remove the failed drive, unscrew it from the caddy, then replace with the new drive. Prior to handling the new drive, ground yourself by touching for example, a radiator

– Open Promise utility and unlock it

– Click on “Physical Drive” list in the Utility and make sure the replacement drive is showing up in the list

– The status of the new drive should be “Unconfigured”

– If the status is “Passthru”, then click on settings for that drive and change it to “Unconfigured”

– Confirm the settings

– Click on “Background Activities”

– Click on the Start button next to Rebuild

– Select the Source drive and the Target drive (usually auto-chosen) and Start the process

– It will take 3-4 hours to complete the process and you can see the progress in the same page

Of course, if you prefer to simply replace your older Pegasus, there are other options out there :


More options for replacing your Raid 5 solution


1. There are several other providers of professional-grade 5-Bay external hard drive enclosures with Raid 5 capability – one of the lower-cost ones is the TerraMaster D5 Thunderbolt 3 Professional-Grade 5-Bay External Hard Drive Enclosure RAID 0/RAID1/RAID5/RAID10 Hard Disk RAID Storage (Diskless). It’s an aluminium case with a handle for easy portablility and 2x Thunderbolt3 / USB-C ports.


Synology DS920+ 4 Bay Desktop NAS Enclosure

2. G-Technology have been around for a long while, and their G-Technology 24 TB G-SPEED Shuttle is expensive, but probably one of the most robust solutions available. The installed drives are SSD, while HDD are supported, and data transfer rate is 2.8 Gbit/s.


G-Technology 24 TB G-SPEED Shuttle SSD 8-Bay Transportable RAID Storage with Thunderbolt 3

3. If you’re happy to forsake the security of Raid 5, you could use an SSD solution from LaCie, and rely on their 5 Year Rescue Data Recovery Services – if your drive fails, send it to them and they’ll fix it. You could combine the use of this SS on a per-project basis, while backing up the media and projects on a daily basis to another usb storage drive.


LaCie 1big Dock 2TB External Solid State Drive NVMe SSD Docking Station – Thunderbolt 3 USB 3.0 7200 RPM

4. If it’s available in your country – the LaCie 84TB 6big Professional RAID Storage for PC and Mac could be the perfect 84TB capacity Raid 5 solution:
– Delivers Thunderbolt 3 speeds for 4K video editing
– Hardware RAID 5/6 for no-compromise data security
– Combines a RAID controller and 7200 RPM HDDs for sustained speeds of up to 1400MB/s turbocharging 4K workflows and file transfers
– Enables videographers to work directly from RAW files and see full-resolution edits in real time
– Daisy-chain up to five Thunderbolt 3. one USB 3.1 or one high-resolution display via a single USB-C cable
– Supports RAID modes 0. 5 and 6

Promise Pegasus 3 R6

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