Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I am running RHEL5 and software RAID (mdadm). Currently I allow the 99-raid-check weekly cron script to run at the normal time (early Sunday morning). However, if the system is off during that time it will run when the system boots with a delay. Looking at the man page for anacrontab and /etc/anacrontab, I can see the current config is set to run every 7 days with a delay of 70 minutes for the cron.weekly scripts. I need to be able to predict when there will be high disk IO, so I want it to run early Sunday morning if it's on, or not at all. My question is, how can I prevent 99-raid-check just to wait until the following week to run and not utilize anacron?

share|improve this question
up vote 0 down vote accepted

The simplest option would be to modify your script to check for I/O load and only run if it is below a threshold. Use something like iostat and add a check in your script that will only run if I/O is below X. You can then leave the cron as is since the script itself will deal with checking the load.

share|improve this answer
thank you for your comment. However this would not fulfill my needs. The IO will spike when mdadm rebuilds the arrays, which is fine, but I want to be able to control the hours that it occurs. – user2789281 Sep 18 '13 at 14:58
@user2789281 if all you want tis for it to run Sunday morning or not at all, just use a normal crontab and give it a specific time. – terdon Sep 18 '13 at 15:02
yes, I think that's exactly what I will do since anacrontab doesn't read crontab. Thanks. – user2789281 Sep 18 '13 at 15:10

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .