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Is anyone else seeing fairly dramatically reduced write performance on softRAID volumes under Tahoe? I have a few different RAID volumes set up - one 2TB RAID 0 in an original 4M2 enclosure, one 3TB RAID 4 in a TB3 Thunderbay Mini, and one 6TB RAID 5 Accelsior 4M2 in a Node Duo, and all are showing write performance 36-37% of previous benchmarks (that is, a reduction of 63-64%). Only the RAID 0 is cracking 500MB/s, with the other two around 400MB/s in Amorphous Disk Mark. The RAID 4 and RAID 5 volumes were both benchmarked at 1100MB/s a month ago, and the RAID 0 at 1400MB/s.
Was there a change in SoftRAID for Tahoe, or are you working around an Apple bug? It's weird that all of my softRAID volumes are so much slower, and by very similar amounts, while my one single drive working volume actually writes a bit faster under 26 than 15.x.
Posted : 23/09/2025 3:07 pm
There is no slowdown under Tahoe.
So there must be another cause. Run Activity Monitor and see if anything is taking disk or CPU activity.
Posted : 23/09/2025 5:53 pm
Topic starter
@softraid-support Found the culprit: I recently got a Thunderbolt 4 monitor with a 4-port USB-A hub, gigabit ethernet, and a USB-C port for daisy-chaining a second display. I have a bunch of external SSDs, but because too many of them are either USB-C or only have one Thunderbolt port, most are chained off of a Caldigit Element Thunderbolt 4 hub, and I had the display plugged into one of the ports on that. The USB-A ports on the monitor take minimal bandwidth, but I think the two 4K displays caused write performance issues on the SSDs that were connected to other TB4 ports on the hub.
Unfortunately, the monitor failed a month after I got it, and the manufacturer does not have replacement units, so I just had to return it as defective. Now that my old OWC Thunderbolt 3 dock is plugged into the Thunderbolt 4 hub (in place of the TB4 monitor), with just one 4K display, ethernet, and low-bandwidth USB-A devices connected to it, my RAID writes are back to normal performance. Looks like that extra stream of 4K video over the single cable pushed things over the edge.
Posted : 29/09/2025 1:42 pm
