Changing DiskSuite Defaults

By default, the DiskSuite configuration defaults to 128 metadevices and state database replicas that are sized to 1034 blocks. The default number of disksets is four. All of these values can be changed if necessary, and the tasks in this section tell you how.

Preliminary Information for Metadevices

• The default number of metadevices for a system is 128. If you need to configure more than the default, you can increase this value up to 1024.

• When you add large numbers of metadevices, you may begin to see some system performance degradation only while administering metadevices (using DiskSuite Tool or the command line utilities). A large number of metadevices should not have an impact on normal system operation.

• If you increase the number of metadevices to gain a larger namespace for partitioning the types of devices within certain numeric ranges, but you create fewer than 128 devices, you should not see any performance degradation. In this case, you should not have to add larger state database replicas.

How to Increase the Number of Default Metadevices (Command Line)

This task describes how to increase the number of metadevices from the default value of 128.

If you lower this number, any metadevice existing between the old number and the new number may not be available, potentially resulting in data loss. If you see a message such as "md: d20: not configurable, check /kernel/drv/md.conf" you will need to edit the md.conf file as explained in this task.

1. After checking the prerequisites ("Prerequisites for Troubleshooting the System") and the preliminary information ("Preliminary Information for Metadevices"), edit the /kernel/drv/md.conf file.

2. Change the value of the nmd field. Values are supported up to 1024.

3. Save your changes.

4. Perform a reconfiguration reboot to build the metadevice names.

   # boot -r

Example -- md.conf File

Here is a sample md.conf file configured for 256 metadevices.

#
#ident "@(#)md.conf   1.7     94/04/04 SMI"
#
# Copyright (c) 1992, 1993, 1994 by Sun Microsystems, Inc.
#
name="md" parent="pseudo" nmd=256 md_nsets=4;

Preliminary Information for Disksets

The default number of disksets for a system is 4. If you need to configure more than the default, you can increase this value up to 32. The number of shared disksets is always one less than the md_nsets value, because the local set is included in md_nsets.

How to Increase the Number of Default Disksets (Command Line)

This task shows you how to increase the number of disksets from the default value of 4.

If you lower this number, any diskset existing between the old number and the new number may not be persistent.

1. After checking the prerequisites ("Prerequisites for Troubleshooting the System"), edit the /kernel/drv/md.conf file.

2. Change the value of the md_nsets field. Values are supported up to 32.

3. Save your changes.

4. Perform a reconfiguration reboot to build the metadevice names.

   # boot -r

Example -- md.conf File

Here is a sample md.conf file configured for five disksets. The value of md_nsets is six, which results in five disksets and one local diskset.

#
#ident "@(#)md.conf   1.7     94/04/04 SMI"
#
# Copyright (c) 1992, 1993, 1994 by Sun Microsystems, Inc.
#
name="md" parent="pseudo" nmd=255 md_nsets=6;

Preliminary Information for State Database Replicas

• If you create large numbers of metadevices, the state database replicas may eventually be too small to contain all the necessary information. If this happens, try adding larger state database replicas by using the -l option to the metadb(1M) command then removing the smaller state database replicas.

• As a general rule, if you've doubled the number of default metadevices, double the size of the state database replicas.

How to Add Larger State Database Replicas (Command Line)

After checking the prerequisites ("Prerequisites for Troubleshooting the System"), and reading the preliminary information ("Preliminary Information for State Database Replicas"), use the metadb command to add larger state database replicas, then to delete the old, smaller state database replicas. Refer to the metadb(1M) man page for more information.

Example -- Adding Larger State Database Replicas

# metadb -a -l 2068 c1t0d0s3 c1t1d0s3 c2t0d0s3 c2t1d0s3
# metadb -d c1t0d0s7 c1t1d0s7 c2t0d0s7 c2t1d0s7

The first metadb command adds state database replicas whose size is specified by the -l 2068 option (2068 blocks). This is double the default replica size of 1034 blocks. The second metadb command removes those smaller state database replicas from the system.