This is on an Xubuntu 20.04 system. I was wondering why I was occasionally seeing a "check" operation occurring on my clean RAID1 mirrors. Eventually I discovered the checkarray and mdcheck scripts in /usr/share/mdadm. It appears that checkarray isn't used (is that correct?), but mdcheck is being launched by /lib/systemd/system/mdcheck_start.service on the first Sunday of each month. I have a couple of questions? 1: Where do you look for the systemctl scheduling of services like this? Is there a cron-like scheduler? The time for this needs to be adjusted. 2: Why does mdcheck get a 6 hour run duration set? Right now it is starting a little after 8 AM, running until 2 PM and then check- pointed and suspended. On Monday at 9:10 AM it continued due to /lib/systemd/system/mdcheck_continue.service. It is running on a 4TB raid that takes over 12 hours to complete, so why stop it after 6 hours? I'm certainly not getting any advantage to running in off hours since it is starting at a really inappropriate time. 3: The process is really putting a load on the system and interfering with other work. Can the priority for this process be lowered so that it doesn't consume so many resources? 4: How critical is the check operation? Does it discover things that the normal RAID operation misses? Anything else I should know about all of this? Thanks. -- Jeffery Small
