3.5.1 Matrix Server Administration Guide

Chapter 7: Configure PSFS Filesystems 108

To take advantage of the DB Optimized performance optimization, an

application’s read or write buffer argument to the read or write system

call must be page-aligned and must be at least a multiple of 512 bytes in

length. Additionally, the target file address (the offset from the beginning

of the file where the I/O will start) must also be a multiple of 512 bytes. If

a transfer does not meet these three requirements, it will be slower.

Applications such as databases that support the use of raw partitions

always follow these constraints.

Unaligned I/Os from applications that support Database Operations are

still allowed, but will be slower. Examples of Database Operations

applications are tools used to back up, copy, and compress database files.

These tools may sometimes issue I/O operations that are not aligned

properly for this performance mount option, but will nonetheless operate

correctly.

The DB Optimized option controls only the way in which database files

are accessed for reads and writes; it does not affect the data itself. You can

switch between the Std. File Optimized and DB Optimized options when

mounting and then remounting a filesystem.

Uses for Filesystems Mounted with DB Optimized

Filesystems mounted with DB Optimized should be used only for

database objects (such as data files, transaction logs, the Oracle OCMS

quorum disk, the Oracle GCS and SPFILE, and so on) and for tools (for

example, backup tools) that manipulate database objects. Database

operational functions such as compressing a tablespace that is being

transported, copying datafiles, and so forth are also supported.

With the DB Optimized mount option, there is no operating system read-

ahead. Tools that perform small I/O requests will execute dramatically

slower on DB Optimized mounted filesystems than on regular mounts.

Tools such as cp(1) and gzip(1), which are used in ancillary database

operations such as relocating archived transaction logs, will suffer. When

possible, use dd(1) with large block-size operations to move files between

DB Optimized mounts and other DB Optimized mounts or regular

mounts. If this is not an acceptable solution, contact PolyServe Technical

Support, as there are several options to address this issue.