I have a server that peforms a resync for its software raid in undefined intervals. This results in massive load and I am forced to stop all services until the resync is complete (20+ hours). What could be the reason for an automatic resync?
In some cases, cron. On RedHat-derived boxes, check for the existence of a file like
Edit following your question: a check is not the same as a resync. A check compares the two halves of a RAID-1 array and updates
If you find the mismatch count is non-zero, you can then choose to force a resync. Your system's script may do that for you as part of the service, I can't comment, but there is a difference between a check and a resync. Both are hugely IO-intensive, though, and result in the sort of performance issues you describe.