SoftRAID (issues)

I guess you need to test with only the M2 on the bus, at least long enough to eliminate "noise" from being part of the problem.

Agreed.

-4x Drives have been certified 3x.
-Initialized
-New volume created via SoftRAID.
-Mounted
-0 errors.

Keep running it now and see if it is stable. then you have a data point to start from, where you can add devices and see if any hardware is triggering problems.

24 hours with no errors (and very little use).

Keep using it, hopefully, your problems will be resolved.

Note: if you have a long cable, use a shorter one for better reliability and faster throughput!

*Also, the 4M2E is daisy chained through a Pegasus3. They are the only 2 units on this TB bus.

We have quite a few Pegasus RAID's at the studio, and have had some very strange issues with them. We've found that the thunderbolt connectors are not to spec, and the official Apple cables are the worst fits. We use cheap aftermarket cables to stop RAID's from hanging systems, randomly disconnecting, and causing data corruption.

Great point.

There is a lot that can cause thunderbolt bus resets, and cables are certainly one of them.

These buses are incredibly fast and it does not take much to create communication issues.

The biggest problem with Thunderbolt cabling is the "feature" that powers off the drives as soon as a cable disconnect is detected, which exasperates this issue.