VERITAS File SystemÖ 3.5 (HP OnlineJFS/JFS3.5) AdministratorÆs Guide (December 2002)

Chapter 9
VERITAS QuickLog
QuickLog Setup
90
Creating a QuickLog Device
The creation of a QuickLog device requires the following two steps:
Step 1. Create a VxVM volume using the command vxassist:
# vxassist -g diskgroup make qlog_volume size vxvm_disk
If the QuickLog volume is a VxVM volume, it must reside in the same disk group as the file system
to be logged. Each QuickLog volume should reside on a separate physical disk. Specify vxvm_disk
during the creation of the VxVM volume to be used by the QuickLog device. The VxVM disk should
not be shared or used by any other volumes.
NOTE As the number of file systems enabled on a QuickLog device increases, the larger the
QuickLog device is, the better the performance will be. Because a QuickLog log file is
circular, very large logs typically reduce the overhead associated with wrapping
when the end of the log file is reached.
To calculate the minimum size of a QuickLog device, determine how many file systems to log to the
device (1-31). Multiply this number by 16 megabytes (16 MB is the optimal VxFS intent log size) to
get the total size of the log area for your QuickLog device. The QuickLog device should be
approximately 50% larger than this QuickLog log area and a minimum of 32 MB. For example, to
estimate the minimum size needed for four file systems on a single QuickLog device:
(4 x 16 MB) x 1.5 = 96 MB
Step 2. Build a QuickLog volume using the command qlogmk:
# qlogmk -g diskgroup vxlog[x] qlog_volume
One to four QuickLog volumes must be attached once you have determined the size of your
QuickLog device. These volumes provide the static storage for the QuickLog device, including the
VxFS log records, QuickLog superblocks and QuickLog maps.
The size of the QuickLog device can be spread out across the one to four QuickLog volumes to be
attached (see “QuickLog Load Balancing” on page 92 for details).
The command qlogmk both writes out the QuickLog volume layout to the volume qlog_volume and
attaches the QuickLog volume to the specified QuickLog device. Acceptable QuickLog device names
are vxlog1 through vxlog31.
Removing a QuickLog Device
The removal of a QuickLog device involves the qlogrm and vxedit commands:
# qlogrm -g diskgroup qlog_volume
qlogrm detaches a QuickLog volume from its QuickLog device. If the QuickLog volume is the only volume
attached to the QuickLog device, all file systems that are logging to the QuickLog device must have logging by
QuickLog disabled prior to using qlogrm (see “Disabling a QuickLog Device” on page 91 for details).
Use vxedit to remove the VxVM volume:
# vxedit -g diskgroup -rf rm qlog_volume