How can I tell what I/O scheduler I'm using on RH4?

[Yong Huang]

On RH5, I can tell what I/O scheduler I'm using:

$ uname -a
Linux thehostname 2.6.18-92.1.13.el5 #1 SMP Thu Sep 4 03:51:21 EDT 2008 x86_64 x86_64 x86_64 GNU/Linux
$ cat /etc/redhat-release
Red Hat Enterprise Linux Server release 5.2 (Tikanga)
$ cd /sys/block/sda/queue
$ ls -l
total 0
drwxr-xr-x 2 root root    0 Nov 26 13:43 iosched
-r--r--r-- 1 root root 4096 Jan 12 23:12 max_hw_sectors_kb
-rw-r--r-- 1 root root 4096 Jan 12 23:12 max_sectors_kb
-rw-r--r-- 1 root root 4096 Jan 12 23:12 nr_requests
-rw-r--r-- 1 root root 4096 Jan 12 23:12 read_ahead_kb
-rw-r--r-- 1 root root 4096 Jan 12 23:12 scheduler
$ cat scheduler
noop anticipatory deadline [cfq]

So I'm using CFQ. But on RH4, there's no /sys/block/sda/queue/scheduler:

$ uname -a
Linux hostname 2.6.9-55.ELsmp #1 SMP Fri Apr 20 16:36:54 EDT 2007 x86_64 x86_64 x86_64 GNU/Linux
$ cat /etc/redhat-release
Red Hat Enterprise Linux AS release 4 (Nahant Update 7)
$ ls -l /sys/block/sda/queue
total 0
drwxr-xr-x  2 root root    0 Jan 13 11:03 iosched
-r--r--r--  1 root root 4096 Jan 13 11:02 max_hw_sectors_kb
-rw-r--r--  1 root root 4096 Jan 13 11:02 max_sectors_kb
-rw-r--r--  1 root root 4096 Jan 13 11:02 nr_requests
-rw-r--r--  1 root root 4096 Jan 13 11:02 read_ahead_kb

I checked grub.conf. Neither box has an entry for I/O scheduler.

Yong Huang