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I've know about running a process under higher & lower priorities for some time, but with different I/O priorities, well that is news to me. My googles have returned information on tools like renice (I've know) and ionice (news to me), but ionice is not on my system, RHEL4.

Question: Does RHEL4 have tools that will let me run a process with low IO priority?

The reason I need this is that running potentially heavy tasks (like du or find/sed against a multi-TB file system) during busy hours (basically waking hours) on the production system could impact performance for tens of minutes or even hours. I'd rather do these whenever it suits me, rather than burning the midnight oil. Again.

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up vote 2 down vote accepted

rhel4 is based on kernel 2.6.9. You'll need at least 2.6.13 to be able to use ionice, and even then that requires you run your lun under the CFQ scheduler.

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OK. Is that that? Or are their other options? – Stu Thompson May 4 '09 at 16:29
Sadly even rhel5 comes with 2.6.18 (plus redhat patches) which will run ionice, but does not support iotop and other useful tools. My advice would be a, use a well tuned array (lots of spindles in raid 10) b, use the deadline io scheduler c, use a well tuned filesystem (this may not be ext3, but that may not be an option if you want to stick with rhel) d, heaps of memory, to cache those dentrys e, if its a dedicated fileserver / nas setup, the consider a different distro (not going to suggest any, for fear of a flame war) with a more recent kernel – Dave Cheney May 5 '09 at 10:06

I've been looking for an ionice(1) equivalent for RHEL4 for a little while myself, especially since I have been using idprio on FreeBSD. Lowering the I/O priority is handy for me when I use VMware's disk manager to create multi-gigabyte virtual disk files. Usually, that causes the load average on the machine to rocket into double digits.

After some Googling around, I found this thread ( and a link to this script:

I have been experimenting with it here, and it seems to do the trick for me. The load average now stays within acceptable levels, and running VMs don't grind to a halt during virtual disk creation.

Hope it helps,
Greg, LLC

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