Configuring a System for GRIO

Caution: The procedure in this section can result in the loss of data if it is not performed properly. It is recommended only for experienced IRIX system administrators. This section describes how to configure a system for GRIO: create an XLV logical volume with a real-time subvolume, make a filesystem on the volume and mount it, and configure and restart the ggd daemon.

1. Choose disk partitions for the XLV logical volume and confirm the hardware configuration as described in the section "Hardware Configuration Requirements for GRIO" in this chapter. This includes modifying the disk drive parameters as described in the section "Disabling Disk Error Recovery" in this chapter.

2. Determine the values of variables used while constructing the XLV logical volume:

   vol_name

   The name of the volume with a real-time subvolume.

   rate

   The rate at which applications using this volume access the data. rate is the number of bytes per time quantum per stream (the rate) divided by 1K. This information may be available in published information about the applications or from the developers of the applications.

   num_disks

   The number of disks included in the real-time subvolume of the volume.

   stripe_unit

   When the real-time disks are striped (required for Video on Demand and recommended otherwise), this is the amount of data written to one disk before writing to the next. It is expressed in 512-byte sectors.

   For non-rotor guarantees:

   stripe_unit = rate * 1K / (num_disks * 512)

   For rotor guarantees:

   stripe_unit = rate * 1K / 512

   extent_size

   The filesystem extent size.

   For non-rotor guarantees:

   extent_size = rate * 1K

For rotor guarantees:

extent_size = rate * 1K * num_disks

opt_IO_size

The optimal I/O size. It is expressed in kilobytes. By default, the possible values for opt_IO_size are 64 (64K bytes), 128 (128K bytes), 256 (256K bytes), and 512 (512K bytes). Other values can be added by editing the /etc/grio_disks file (see the section "/etc/grio_disks File Format" in this chapter for more information).

For non-rotor guarantees, opt_IO_size must be an even factor of stripe_unit, but not less than 64.

For rotor guarantees opt_IO_size must be an even factor of rate. Setting opt_IO_size equal to rate is recommended.

Table 9-3 gives examples for the values of these variables.

Examples of Values of Variables Used in Constructing an XLV Logical Volume Used for GRIO

Variable	Type of Guarantee	Comment	Example Value
vol_name	any	This name matches the last component of the device name for the volume, /dev/dsk/xlv/vol_name	xlv_grio
rate	any	For this example, assume 512 KB per second per stream	512
num_disks	any	For this example, assume 4 disks	4
stripe_unit	non-rotor	512*1K/(4*512)	256
	rotor	512*1K/512	1024
extent_size	non-rotor	512 * 1K	512k
	rotor	512 * 1K * 4	2048k
opt_IO_size	non-rotor	128/1 = 128 or 128/2 = 64 are possible	64
	rotor	Same as rate	512

1. Create an xlv_make script file that creates the XLV logical volume. (See the section "Creating Volume Objects With xlv_make" in Chapter 7 for more information.) Example 9-1 shows an example script file for a volume.

   Example 9-1 : Configuration File for a Volume Used for GRIO

# Configuration file for logical volume vol_name. In this
# example, data and log subvolumes are partitions 0 and 1 of
# the disk at unit 1 of controller 1. The real-time
# subvolume is partition 0 of the disks at units 1-4 of
# controller 2.
# 
vol vol_name 
data 
plex 
ve dks1d1s0 
log 
plex 
ve dks1d1s1 
rt 
plex 
ve -stripe -stripe_unit stripe_unit dks2d1s0 dks2d2s0 dks2d3s0 dks2d4s0 
show 
end 
exit 

1. Run xlv_make to create the volume:

   # xlv_make script_file

   script_file is the xlv_make script file you created in step 3.

2. Create the filesystem by giving this command:

   # mkfs -r extsize=extent_size /dev/dsk/xlv/vol_name

3. To mount the filesystem immediately, give these commands:

   # mkdir mountdir

   # mount /dev/dsk/xlv/vol_name mountdir

   mountdir is the full pathname of the directory that is the mount point for the filesystem.

4. To configure the system so that the new filesystem is automatically mounted when the system is booted, add this line to /etc/fstab:

   /dev/dsk/xlv/vol_name mountdir xfs rw,raw=/dev/rdsk/xlv/vol_name 0 0

5. If the file /etc/grio_config exists, and you see OPTSZ=65536 for each device and OPTSZ=524288(check this) for disks in the real-time subvolume, skip to step 10.

1. Create the file /etc/grio_config with this command:

   # cfg -d opt_IO_size

2. If you want soft rate guarantees, edit /etc/grio_config and remove this string:

   RT=1

   from the lines for disks where software retry is required (see the section "/etc/grio_config File Format" in this chapter for more information).

3. Restart the ggd daemon:

   # /etc/init.d/grio stop

   # /etc/init.d/grio start

   Now the user application can be started. Files created on the real-time subvolume volume can be accessed using guaranteed-rate I/O.