Creating volumes 257

Creating tagged volumes

RAID-5 logs can be concatenated or striped plexes, and each RAID-5 log associated with a RAID-5 volume has a complete copy of the logging information for the volume. To support concurrent access to the RAID-5 array, the log should be several times the stripe size of the RAID-5 plex.

It is suggested that you configure a minimum of two RAID-5 log plexes for each RAID-5 volume. These log plexes should be located on different disks. Having two RAID-5 log plexes for each RAID-5 volume protects against the loss of logging information due to the failure of a single disk.

If you use ordered allocation when creating a RAID-5 volume on specified storage, you must use the logdisk attribute to specify on which disks the RAID- 5 log plexes should be created. Use the following form of the vxassist command to specify the disks from which space for the logs is to be allocated:

#vxassist [-b] [-g diskgroup] -o ordered make volume length \ layout=raid5 [ncol=number_columns] [nlog=number] \ [loglen=log_length] logdisk=disk[,disk,...] storage_attributes

For example, the following command creates a 3-column RAID-5 volume with the default stripe unit size on disks mydg04, mydg05 and mydg06. It also creates two RAID-5 logs on disks mydg07 and mydg08.

#vxassist -b -g mydg -o ordered make volraid 10g layout=raid5 \ ncol=3 nlog=2 logdisk=mydg07,mydg08 mydg04 mydg05 mydg06

Note: The number of logs must equal the number of disks specified to logdisk.

For more information about ordered allocation, see “Specifying ordered allocation of storage to volumes” on page 245 and the vxassist(1M) manual page.

If you need to add more logs to a RAID-5 volume at a later date, follow the procedure described in “Adding a RAID-5 log” on page 283.

Creating tagged volumes

Volume tags are used to implement the Dynamic Storage Tiering feature of the Storage Foundation software. For more information about this feature, see the Veritas File System Administrator’s Guide.

You can use the tag attribute with the vxassist make command to set a named tag and optional tag value on a volume, for example:

#vxassist -b -g mydg make volmir 5g layout=mirror tag=mirvol=5gTo list the tags that are associated with a volume, use this command:#vxassist [-g diskgroup] listtag volumeTo list the volumes that have a specified tag name, use this command:
# vxassist [-g diskgroup] list tag=tagname volume