mdadm - How to Pause a "CHECK" sync_action?
Once in a while, server administrators can initiate a "CHECK" sync_action on their array. This can be accomplished with the following command:
This will have mdadm immediately start a "check" process on the array to verify that all parity is correct. It is a good way to ensure the array is healthy, and that there are no underlying errors on any of the drives affecting your data. CarefuL: On large arrays (++TB), this check can take days!
sudo su -
echo check >> /sys/block/md0/sync_action
Typically, one might decided to schedule these checks using a cron entry. Perhaps once a month, we'll have this run.
* Is there any way to "PAUSE" this mdadm check process? Or stop it?
It is unfortunate if you've brought your server to a LAN party to host files, and all of a sudden the CHECK is running (oops I forgot it's the XX day of the month and the cron kicked in). Sometimes there are situations where you just don't want it to run and it's already started! (i..e you would notice because there is a huge performance impact on CPU and I/O.)