# How to start using GEOM_SCHED?



## terminus (Jul 30, 2010)

Hi all,

I have just installed FreeBSD 8.1-RELEASE (later upgraded to 8-STABLE). I want to start using new fancy feature named GEOM_SCHED - GEOM I/O sheduler.

So I red man for gsched and try to do this:

```
gsched insert -a rr /dev/ad4
```
After that "gsched status" shows that there is new ad4.sched. provider, and all looks OK. But, unfortunately, then system restarts, this ad4.sched. disapers and "gsched status" shows nothing. The same thing happens with "gsched create" - I can see new ad4.sched. device under /dev, but after reboot it's gone.

Both geom_sched.ko and gsched_rr.ko modules loaded from loader.conf.
I been trying to do it in both "normal"/"single user" modes - no luck.

Any idea how to start using GOEM_SCHED? Should I try to make ad4.sched. durind installation (from emergency shell) and try to install system afterwards?


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## lily (Jul 30, 2010)

Since gsched doesn't store metadata on disks I don't think it requires to be permanently enabled. It would still be useful to enable it from a kernel environment via loader.conf so that it's available during boot and in single user mode. But for now you can use rc.d script, e.g.
	
	



```
#! /bin/sh

# REQUIRE: FILESYSTEMS
# PROVIDE: geom_rr

. /etc/rc.subr

name=geom_rr

start_cmd=${name}_start
stop_cmd=:

geom_rr_start() {
	geom sched insert -a rr ada0
	geom sched insert -a rr ada1
}

run_rc_command "$1"
```


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## terminus (Jul 30, 2010)

Thanks - it answers the question.
I did not known what gshed do not stores any metadata on GEOM providers...
:\


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