Pegasus32 R8 32TB RAID5: Expected speeds to an Apple Mac Studio (M1 Max)? And...

  • Last Post 29 June 2023
Jim Feeley posted this 13 June 2023

I'm looking to buy a 32TB (or so) storage system this week. The Pegasus32 R8 is one of three systems I'm considering. This will be used for video editing. I'd like to place the storage system on a tray under my edit desk. The answer to two questions will be really helpful as I choose a system. 

1) What are the expected sustained write and read speeds from a 32TB Pegasus32 configured in RAID5 with 4TB HHDs (ie- your standard configuration) over Thunderbolt 3 to a Mac Studio with a M1 Max processor? I'm especially interested in the numbers generated by Blackmagic's or AJA's drive test applications. 

1a.- Are there noticable differences in write and read speeds when using an Intel-based Mac compared to using an Apple Silicon-based Mac?

2) If I use a good-quality 100W Thunderbolt 3 cable that's about two meters long, will I notice significantly lower write and read speeds? (Or is there another type of Thunderbolt 3 cable that I could use?)

2a.- If so, what is the maximum length cable I can use without degrading performance more than say 5%? 



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R P posted this 14 June 2023

Hi Jim,


I ran Black Magic Disk Speed Test on a Pegasus 32 R8 on both an M1 Mac mini and a 2019 Mac Pro.

Computer BlackMagic Writes BlackMagic Reads
M1 Mac Mini ~1650 MB/s ~1300 MB/s
2019 Mac Pro ~1650 MB/s ~1300 MB/s

The Black Magic numbers jump around a bit, but they seem more or less the same.

Note that some applications can degrade performance.


It depends on the what type of cable you get. I think Startech sums it up clearly.

  • Active Thunderbolt 3 cables support Thunderbolt at 40Gbps data transfer at lengths of up to 2m. Optical cables are targeted later, with lengths of up to 60m. Passive lower cost cables are only capable of 20Gbps data transfer at 1m or 2m lengths, but can achieve the full 40Gbps at a shorter cable length of 0.5m

Optical cables are available now, but they are expensive


For full ThunderBolt 3 transfer rates with a 2m cable you'll need an active cable. Be advised that not all cables support 100W charging.

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R P posted this 14 June 2023

Hi Jim,

Is this the correct and compatible model for the current Pegasus32 32TB system?

This drive should be fine.

It's a great idea to have a spare drive onhand.

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Jim Feeley posted this 14 June 2023

RP, that's a super useful response! Thanks for your work to get those numbers. You convinced me to buy the system I asked about.

One last thing: I'd like to have a spare drive and carrier on hand. Just in case...

Is this the correct and compatible model for the current Pegasus32 32TB system?


Thanks a bunch!

Jim Feeley posted this 29 June 2023

Followup: I've now had the Pegasus32 33TB system for a couple weeks. Blackmagic Disk Speed Test shows me getting about 1400MB/s writes and about 1350MB/s reads on my Mac Studio M1 Max (slightly different numbers from what RP found, but I've found Disk Speed Test to vary a bit). That's more than good enough performance for my needs.

Also, I get basically the same speeds with a two-meter cable as I do with the 0.7-meter (or so) cable that Promise ships with the drive. HOWEVER... The first two-meter cable I tried didn't work. The Mac detected the drive, but the drive wouldn't mount. The cable's specs fit what was needed; I don't know if just that cable is flawed or if the brand isn't reliable.

So I then tried a cable from OWC, specifically the "2.0M (78") OWC Thunderbolt (USB-C) Cable." That cable cost about the same amount as the one that didn't work, and again it delivers the same write and read performance as the short cable that ships with the drive.

So far, I'm very happy with the Pegasus32 RAID. And I expect to be into the future.