July 25 - 2021. I have restored the speed on my 20TB 5BIG by converting the whole box to OWC SoftRaid PRO. After LaCie fixed the driver and allowed the drive to mount, I was getting speeds in the order of 49 MB/sec write and 225 MB/sec read ..... after converting to SoftRaid, with a the RAID loaded to about 75% of its capacity I am getting speeds in the 300 / 500 range. Reply if you want details. jc

There is another thread, below, discussing this topic. We are trying to get as many people affected to reply/post there, instead, so we may begin to build a compelling case to LaCie to acknowledge and address this issue. Please check out.... https://discussions.apple.com/thread/252212343?login=true&page=2 jc

April 8 - 2021. 5 few days ago I received a notice that LaCie had issued an update to the LaCie RAID manger that would work under Big Sur 11.2.3. Today, April 8th, I set aside the afternoon to download and install the RAID driver and physically move my 5BIG from my Intel Mac Pro 6,1 (2013) Thunderbolt-2 to my Mac Mini M1 (16GB ram/2TB storage). So this is LaCie Raid Manager 2.9.3.207. This time the install under Big Sur went fine - I had to approve the software's source with Privacy as expected and this time it went okay. The drive was recognized and I could read and write to it. However, it's performance is seriously impacted. On my Intel MacPro (TrashCan 6,1 Thunderbolt 2) I get at least, 400/400 MB/sec by any measure (transfer a really big video file and stopwatch it, Blackmagic, etc) - but on moving the drive to the M1 my speeds are roughly write 55MB/sec; read 270 MB/sec...there is some variability but this is the essence of it - not much better than a USB2 drive and on par with a FW 800. So this is a serious problem. This drive, while readable, is useless for ay serious photographic/video work. I spent some hours on the phone with tech support today and they do not have an answer for this. I swapped every TB2 cable and Apple adapter I have* - so it's not a cable or adapter issue. It's a driver issue - entangled with caches/buffers/optimization and all that. I have 3 Apple TB 2--3 dongles I have 2M and half-metre cables from different manufacturers - I counter-swapped, and all these work fine on the TrashCan - and when connected on the clearest/simplest path on the M1 Mac - much less performance. Two questions what numbers are you seeing* How do we mount a claim on this. the reason I am asking this is if your 5Big (whatever) is performing differently than mine - I have done 2 failed drive swaps over the years and although I have replaced with IronWolf, maybe I have introduced something incompatible or less optimized. Nonetheless, the LaCie Techs cannot discern this and the drive currently does do 400+/400+ on the Intel and 55/270 on the M1. I do not relish dumping this drive system - but it is useless on the new future of Macs. The LaCie tech sort-of admitted to this but has no solution and so we must apply some pressure. Nest Steps. BTW - I am sure this applies to 6Big and 12Big as well....so this is not a small community that has had their hardware back-watered very prematurely. jc - April 8-2021