Superslow write speeds Pegasus2 R6

  • Last Post 17 April 2020
Aron Liedtke posted this 31 March 2020

Takes over 10min to copy a couplle of hundred megabytes to the R6 from my MBP 16", was the same storry with my MBP 15". 

R6 is in raid5 and i have 6 TOSHIBA DT01ACA2 Drives. All system statuses are OK in Promise Utility.

The R6 is plugged in directly to my MBP with an original TB3 to TB2 dongle from Aplle and i have nothing daisy chained. 

My computer spec is:  MacBook Pro (16-inch, 2019), 2TB ssd, 2,4 GHz 8-Core Intel Core i9, 32 GB 2667 MHz DDR4, AMD Radeon Pro 5500M 8 GB Intel UHD Graphics 630 1536 MB, 

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Sean Lander posted this 07 April 2020

I am seeing similar behaviour ever since upgrading to Mac OS Catalina.
Read speeds on my R4 have fallen from about 500MB/s to 100MB/s

Sean Lander posted this 08 April 2020

Just installed the latest update to Catalina and now speeds are much faster. Read speeds are closer to 500MB/s.
So it was a Mac OS issue.

Preston Laura posted this 11 April 2020

It's setup RAID 5, 4x7200 2 TB drives, no other thunderbolt peripherals and the internal drive is giving around 100MB/s solid read and write upsers. Tested it on a MacBook Air with similar results so it isn't the Mac.

Raghuraman Kannan posted this 14 April 2020

Hi ,

In order to find the exact problem please register yourself as a user @ and open a case with  latest subsystem report.

Steps to save the subsystem report :

1) Open Promise Utility.

2) Click subsystem information icon on the top of the window.

3) Click the lock symbol on the left bottom corner of the screen to unlock the utility.

4) Click on save service report button to save the subsystem report and attach it to the case


Thanks !

Aron Liedtke posted this 15 April 2020

4) Click on save service report button to save the subsystem report and attach it to the case



Thanks Raghuraman!

I tried to go in to promise utility and "Save a service report" but it won't create one for me. There is a "wheel" spining for about a quarter of a second and then nothing happens. Or am i missing something and it's actually automatically saved somewhere?


I opened a case nonetheless.


It's actually even worse than what i first described. its almost unusable. It takes up to a minute sometimes to just create a folder on the R6!!… On Black magic disk speed test i get write speeds of about 0.1-0.5 Mb/s 




Raghuraman Kannan posted this 17 April 2020

Hi Aron,

Please check the below link and make sure you have the correct settings.  Also, make sure you have the Cache settings set to "ReadAhead/WriteBack".

In the meantime, please wait for us to check the case and respond to you.

Thanks !

Aron Liedtke posted this 17 April 2020

Hi Raghuraman,

Wasn't sure about the Cache settings set to "ReadAhead/WriteBack". i could find this: AdaptiveWBCache: Disabled 

Other than that settings in the link was correct.


Best, A