QuasarDB cluster stuck in IOWAIT on AWS EC2 instances
(Disclaimer: I work at QuasarDB)
Because you are using the newer gp3 EBS volume types, and you are reporting a system-wide instability of the system (rather than just the QuasarDB process), I believe this is related to the EBS volume types, rather than something related to QuasarDB.
We have observed stability issues with gp3 volumes under high pressure ourselves, with a system getting stuck. To the best of our understanding, this is related to an EBS host-level driver. GP3 instability have been report by others as well.
What I would recommend is to use the older GP2 EBS volume types, and see if that solves the issue. If you would still like to achieve high-throughput, you can combine multiple GP2 EBS volumes using mdraid as recommended by AWS themselves.