As the Dell forums are a veritable disaster I'm trying here in case somebody has some hints for me here :)
We have a system with 3 drives:
- SSD for the OS
- SSD containing a ZFS pool backing LXD containers
- A "backup" storage HDD drive
The system is running Ubuntu Bionic.
Now these area all connected to the PERC controller in a non-raid configuration. All firmware is up to date on the server.
What we are seeing is when we stream data to the HDD drive using rsync or ftp from remote network storage, the write operations to the HDD drive slows down the entire system
It is as if high IOwait on the HDD drive blocks IO operations on the SSD drives. Which to me is highly counter-intuitive.
Why would write operations to the HDD drive cause the entire system to lock up and slow down access times on the SSD drives? Is the controller at fault, or are there some knobs in the Linux Kernel which can be turned here?
Did I shoot myself in the foot by mixing in an HDD drive with my SSD drives? :)