HP-UX VxFS tuning and performance - filibeto.org
HP-UX VxFS tuning and performance - filibeto.org
HP-UX VxFS tuning and performance - filibeto.org
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Underst<strong>and</strong>ing <strong>VxFS</strong><br />
In order to fully underst<strong>and</strong> some of the various file system creation options, mount options, <strong>and</strong><br />
tunables, a brief overview of <strong>VxFS</strong> is provided.<br />
Software versions vs. disk layout versions<br />
<strong>VxFS</strong> supports several different disk layout versions (DLV). The default disk layout version can be<br />
overridden when the file system is created using mkfs(1M). Also, the disk layout can be upgraded<br />
online using the vxupgrade(1M) comm<strong>and</strong>.<br />
Table 1. <strong>VxFS</strong> software versions <strong>and</strong> disk layout versions (* denotes default disk layout)<br />
OS Version SW Version Disk layout version<br />
11.23 <strong>VxFS</strong> 3.5<br />
<strong>VxFS</strong> 4.1<br />
<strong>VxFS</strong> 5.0<br />
11.31 <strong>VxFS</strong> 4.1<br />
<strong>VxFS</strong> 5.0<br />
<strong>VxFS</strong> 5.0.1<br />
3,4,5*<br />
4,5,6*<br />
4,5,6,7*<br />
4,5,6*<br />
4,5,6,7*<br />
4,5,6,7*<br />
Several improvements have been made in the disk layouts which can help increase <strong>performance</strong>. For<br />
example, the version 5 disk layout is needed to create file system larger than 2 TB. The version 7 disk<br />
layout available on <strong>VxFS</strong> 5.0 <strong>and</strong> above improves the <strong>performance</strong> of large directories.<br />
Please note that you cannot port a file system to a previous release unless the previous release<br />
supports the same disk layout version for the file system being ported. Before porting a file system<br />
from one operating system to another, be sure the file system is properly unmounted. Differences in<br />
the Intent Log will likely cause a replay of the log to fail <strong>and</strong> a full fsck will be required before<br />
mounting the file system.<br />
Variable sized extent based file system<br />
<strong>VxFS</strong> is a variable sized extent based file system. Each file is made up of one or more extents that<br />
vary in size. Each extent is made up of one or more file system blocks. A file system block is the<br />
smallest allocation unit of a file. The block size of the file system is determined when the file system is<br />
created <strong>and</strong> cannot be changed without rebuilding the file system. The default block size varies<br />
depending on the size of the file system.<br />
The advantages of variable sized extents include:<br />
Faster allocation of extents<br />
Larger <strong>and</strong> fewer extents to manage<br />
Ability to issue large physical I/O for an extent<br />
However, variable sized extents also have disadvantages:<br />
Free space fragmentation<br />
Files with many small extents<br />
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