VERITAS File System 3.5 (HP OnlineJFS/JFS 3.5) Administrator's Guide (August 2003)

Chapter 2
VxFS Performance: Creating, Mounting, and Tuning File Systems
Choosing mount Command Options
35
ioerror
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 while reading or writing metadata. The file system can respond to these I/O errors either by
halting or by gradually degrading. The ioerror option provides four policies that determine how the file
system responds to the various errors. All four policies limit data corruption, either by stopping the file
system or by marking a corrupted inode as bad. The four policies are disable, nodisable, wdisable, and
mwdisable
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 is sufficient 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.
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.
For file data read and write errors, VxFS sets the VX_DATAIOERR flag in the superblock. For metadata read
errors, VxFS sets the VX_FULLFSCK flag in the superblock. For metadata write errors, VxFS sets the
VX_FULLFSCK and VX_METAIOERR flags in the superblock and may mark associated metadata as bad on
disk. VxFS then prints the appropriate error messages to the console (see Appendix B, “Kernel Messages,” on
page 91 for information on actions to take for specific errors).
You should stop the file system as soon as possible and repair the condition causing the I/O error. After the
problem is repaired, run fsck and mount the file system again. Select nodisable if you want to implement
the policy that most closely resembles the previous VxFS error handling policy.
If wdisable (write disable) or mwdisable (metadata-write disable) is selected, the file system is disabled or
degraded, depending on the type of error encountered. Select wdisable or mwdisable for environments where
read errors are more likely to persist than write errors, such as when using non-redundant storage.
mwdisable is the default ioerror mount option for local mounts. See the mount_vxfs (1M) manual page for
more information.
largefiles | nolargefiles
VxFS supports files up to two terabytes in size.
NOTE Be careful when enabling large file capability. Applications and utilities such as backup may
experience problems if they are not aware of large files.
Creating a File System with Large Files
You can create a file system with large file capability by entering the following command:
# mkfs -F vxfs -o largefiles special_device size
Specifying largefiles sets the largefiles flag, which allows the file system to hold files up to two terabytes
in size. Conversely, the default nolargefiles option clears the flag and prevents large files from being
created:
# mkfs -F vxfs -o nolargefiles special_device size
NOTE The largefiles flag is persistent and stored on disk.