Veritas File System 5.0 Administrator's Guide (September 2006)
specify the O_SYNC fcntl in order to write the file data synchronously. However,
this has the undesirable side effect of updating inode times and therefore slowing
down performance. The convosync=dsync, convosync=unbuffered, and
convosync=direct modes alleviate this problem by allowing applications to take
advantage of synchronous writes without modifying inode times as well.
Before using convosync=dsync, convosync=unbuffered, or convosync=direct,
make sure that all applications that use the file system do not require synchronous
inode time updates for O_SYNC writes.
The ioerror mode
This mode sets the policy for handling I/O errors on a mounted file system. I/O
errors can occur while reading or writing file data or metadata. The file system
can respond to these I/O errors either by halting or by gradually degrading. The
ioerror option provides five policies that determine how the file system responds
to the various errors. All policies limit data corruption, either by stopping the file
system or by marking a corrupted inode as bad.
The policies are the following:
■ disable
■ nodisable
■ wdisable
■ mwdisable
■ mdisable
The disable policy
If disable is selected, VxFS disables the file system after detecting any I/O error.
You must then unmount the file system and correct the condition causing the I/O
error. After the problem is repaired, run fsck and mount the file system again.
In most cases, replay fsck to repair the file system. A full fsck is required only
in cases of structural damage to the file system's metadata. Select disable in
environments where the underlying storage is redundant, such as RAID-5 or
mirrored disks.
The nodisable policy
If nodisable is selected, when VxFS detects an I/O error, it sets the appropriate
error flags to contain the error, but continues running. Note that the degraded
condition indicates possible data or metadata corruption, not the overall
performance of the file system.
VxFS performance: creating, mounting, and tuning file systems
Choosing mount command options
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