qioadmin

NAME

qioadmin - VxFS Quick I/O for Databases cache administration utility

SYNOPSIS

AVAILABILITY

VRTSvxfs

DESCRIPTION

The VERITAS Quick I/O for Databases feature combines the advantages of raw I/O and file I/O to improve database transaction processing performance. Cached Quick I/O further improves database performance on machines with sufficient memory by caching data in the file system cache. On 32-bit systems, for example, databases can only use up to 4 GB of the memory for their database cache because of the 32-bit address space limitation, so for read operations, Cached Quick I/O stores database blocks in file system cache. This reduces the number of physical I/O operations required.

On 64-bit systems, where limited memory addressing is not a critical problem, using the file system caching still increases performance by taking advantage of the read-ahead functionality. To maintain the correct data in the buffer for write operations, Cached Quick I/O keeps the buffer cache in sync with the data written to disk.

mount_point can be either a prefix to a relative path name when qiotab is not specified, or can select a particular device in qiotab.

ENABLING CACHING

There are two components to enabling Cached Quick I/O. First, caching must be enabled on the file system, second, caching must be enabled on individual files in the file system. By default, Cached Quick I/O on a file system is initially disabled.

You can enable Cached Quick I/O on a file system by setting the tunable parameter qio_cache_enable=1 of vxtunefs (see the vxtunefs(1M) manual page). After setting the qio_cache_enable parameter, caching is enabled for all files in the file system. You can then turn caching off, or on again, on a per-file basis using qioadmin . The qio_cache_enable parameter is not persistent across mounts, returning to its default value when the file system is unmounted. You can make the qio_cache_enable parameter persistent across mounts by modifying the tunefstab file (see the tunefstab(4) manual page).

The qioadmin cache advisories operate only if Cached Quick I/O is enabled for the file system. If the qio_cache_enable flag is zero, Cached Quick I/O is OFF for all the files in that file system even if the individual file cache advisory for a file is ON. The per-file cache advisories are not persistent across mounts, returning to their default values when the file system is unmounted. You can use the qiotab file to make the cache advisory settings permanent.

For more information on how to use Cached Quick I/O, see the VERITAS File System Administrator's Guide and the VERITAS Storage Foundation for databases documentation.

QIOTAB FORMAT

/etc/vx/qioadmin is the default qiotab file for Cache Quick I/O advisories. When the file system is mounted, entries in /etc/vx/qioadmin are processed and the advisories are set on the listed files. qiotab contains a series of entries in the format shown below.

device=block_device 

Where block_device is the block device used to mount a file system.

The device= entry indicates the start of files belonging to a particular file system. All the files that follow the device= entry belong to the file system mounted on the specified device. The second device= entry delineates the end of files on one device and the start of files on another device. The following qiotab example shows the list of files to cache in the file systems /database01 and /database02 .

CLUSTER FILE SYSTEM ISSUES

Quick I/O works on VxFS cluster file systems, but Cached Quick I/O is not currently supported.

OPTIONS

The default behavior is to set the caching advisories on a file system from the default qiotab file /etc/vx/qioadmin .

-p " listfile"

Prints the caching advisories for the files listed in the file listfile . The file names can be path names relative to the mount point or absolute path names.

-P " filename,..."

Prints the current caching advisories for the files listed on the command line. The file names can be path names relative to the mount point or absolute path names.

-s qiotab

Sets the caching advisories on the files based on entries in qiotab. If a mount_point is specified, -s selects a particular device and all associated files from the qiotab file. If no mount_point is specified, -s selects all devices and associated files listed in the qiotab file.

-S filename={ON|OFF|on|off}...

Sets the caching advisories using the list of files from the command line. filename can be an absolute path name or a path name relative to the mount point. Setting the value to ON (or on ) turns on caching if the qio_cache_enable option of vxtunefs is set for the file system. Setting it to OFF (or off ) turns caching off.

FILES

/etc/vx/qioadmin

Default qiotab file.

SEE ALSO

qiomkfile (1), qiostat (1), vxtunefs (1M)

The VERITAS File System Administrator's Guide and the VERITAS Storage Foundation for databases documentation. have more detailed information.