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How To Upgrade Promise Pegasus Thunderbolt RAID With New Drives

Promise Pegasus R4

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 6tb drives are readily available.

I also came to the decision to install larger drives due to the Thunderbolt limitation of only being able to daisychain 6 units, and not being able to find a Thunderbolt dock that would multiply the number of ports (2) available on my iMac. I have 6 RAIDS attached already, so upgrading them internally is my most cost-effective option.

So 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 backups, without problems, so thought these would be a good bet.

So, 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 Western Digital. Promise have 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 drives in a RAID:

  • all drives should be the same capacity and ideally be identical drives; if you put a 4tb drive in a RAID where the other drives are 2tb, that 4tb drive will only show up as 2tb
  • 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 is the Toshiba 4TB 7200 rpm 3.5″ – internal hard drive – click the image to purchase it on Amazon UK.

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