One drive out of 6 has gone critical 24TB Array

  • Last Post 14 July 2019
Larry Warner posted this 13 July 2019

I'm no tech wizard, but my top drive out of 6 has gone "critical" according to your Promise Utility App.  I can still access the data apparently, but I am concerned it is going to fail.  I own this unit:  Promise Technology Pegasus3 R6 PC Edition 24TB 6-Bay Thunderbolt 3 RAID Array (6 x 4TB)

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Larry Yaeger posted this 14 July 2019

You should replace that drive immediately.  (Well, first make sure the door hasn't simply been popped open or something by accident, but I think "critical" is different from missing.  I only mention it because I had this happen once to me in the bottom drive, when the latch got bumped by something in front of the unit.)

You don't say what RAID level you're using.  If it's the default RAID 5 you can only afford to lose 1 drive, but as long as you swap in a good replacement for that failing drive, all your data should be protected and the Pegasus3 will repopulate the new drive so the entire array is protected.  (I use RAID 6, because I want the data to be okay even if two drives fail.)

You can download a compatibility guide for your particular unit from the downloads area here:

Specifically, I think the current compatibilty guide for your unit is here:

It looks like you can replace your 4TB drive with either: Toshiba MD04ACA400 or Toshiba MG04ACA400E. I don't know what difference that "E" makes.

I'm just a fellow user of Promise Pegasus technology, not an affiliate of the company.

Larry Warner posted this 14 July 2019



I'm no tech wizard, I just used the tools that Promise provided to set up the array.  So I can't tell you the RAID configuration.  It's whatever is the least resistance on getting the array up and running with the Promise App. 

I am able to access the data, even with my number one drive failure.  I backed up what was truly important (backups of client project video still in progress, and a couple of projects I am working on) and took the whole array out of service.

I was able to start an RMA - which means Promise will replace the defective drive.  The unit is under a three year warranty, and I have a couple of years left on the warranty.  I'm hoping that there are no issues when I replace the drive. 

Larry Yaeger posted this 14 July 2019

I'm glad Promise is replacing the drive for you. Hope it gets there quickly.

BTW, I think that extra "E" in the model number is for "Enterprise", which should be a more reliable drive with a longer lifetime. But either should do.

I know Promise ships Pegasus3 R8 models as RAID 5, which offers one-disk redundancy. I'm sufficiently paranoid about my data I converted to RAID 6, which offers two-disk redundancy. The first time I did it, the instructions were pretty bad, and it's not at all obvious how to do it in the software. You have to delete the data array (which sounds hecka scary, I know), and recreate it from scratch. I've got straightforward instructions for how to do it now, that I can share if you want, but it sounds like you don't want to mess with it too much. Good luck.