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CIO/DIO and JFS2 read ahead

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Operating Systems AIX CIO/DIO and JFS2 read ahead
# 8  
Old 11-14-2008
pstat -a shows, like for example ps aux, only the number of current started aioservers, but not if they are busy or not. With nmon shift+a you see how many are really currently busy and this is on system with an app using AIO, going up and down. Often the maxreqs is forgotten to be configured somewhat large too so the app doesn't get errors regarding to hit the max of queued AIO requests (some "error 5" in Oracle for example).

Nevertheless, we will have to check out if the OP needs AIO at all, which he could and should find out. Maybe he uses it already, no idea. Maybe he offers us some more info to help him.
In our environments I used CIO as a kind of last ressort of tuning, when everything else with AIO and ioo tuning didn't help anymore.
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LEARN ABOUT REDHAT

mkfs.jfs

mkfs.jfs(8)						     JFS file system creation						       mkfs.jfs(8)

NAME

       mkfs.jfs - create a JFS formatted partition

SYNOPSIS

       mkfs.jfs [options] device

DESCRIPTION

       mkfs.jfs is used to create (format) a JFS partition.  mkfs.jfs must be run as root.

       device is the special file name corresponding to the actual device (e.g. /dev/hdb1) on which a JFS file system will be created.

       The default block size is 4096.

WARNING

       mkfs.jfs will destroy all data on the specified device!

OPTIONS

       -c     Check the device for bad blocks before building the file system.

       -L volume_label
	      Set the volume label for the file system.

       -O     Provide case-insensitive support for compatibility with OS/2.

       -q     Quiet execution - do not ask for confirmation before creating the file system.

       -s log_size
	      Set the log size (in megabytes).	If the -s option is not used, the default log size is 0.4% of the aggregate size.

       -V     Print version information and exit (regardless of any other chosen options).

EXAMPLES

       Format 3rd partition on 2nd hard disk with the volume label "JFS_hdb3":

	      mkfs.jfs -L JFS_hdb3 /dev/hdb3

       Format 5th partition on 1st hard disk, verifying each block created:

	      mkfs.jfs -c /dev/hda5

REPORTING BUGS

       If you find a bug in JFS or mkfs.jfs, please report it via the bug tracking system ("Report Bugs" section) of the JFS project web site:
       http://oss.software.ibm.com/jfs

       Please  send as much pertinent information as possible including any error messages resulting from running mkfs.jfs and the complete output
       of running fsck.jfs with the -v option.

SEE ALSO

       mkfs(8), fsck.jfs(8), extendfs(8), logdump(8), logredo(8), xchkdmp(8), xpeek(8)

AUTHORS

       Barry Arndt  (barndt@us.ibm.com)
       William Braswell, Jr.

       mkfs.jfs is maintained by IBM.
       See the JFS project web site for more details:
       http://oss.software.ibm.com/jfs/

								 November 9, 2001						       mkfs.jfs(8)