VERITAS File System 4.1 Administrator's Guide

VxFS Performance: Creating, Mounting, and Tuning File Systems
Choosing mount Command Options
Chapter 2 43
nodatainlog
Use the nodatainlog mode on systems with disks that do not support bad block revectoring.
Usually, a VxFS file system uses the intent log for synchronous writes. The inode update and
the data are both logged in the transaction, so a synchronous write only requires one disk
write instead of two. When the synchronous write returns to the application, the file system
has told the application that the data is already written. If a disk error causes the metadata
update to fail, then the file must be marked bad and the entire file is lost.
If a disk supports bad block revectoring, then a failure on the data update is unlikely, so
logging synchronous writes should be allowed. If the disk does not support bad block
revectoring, then a failure is more likely, so the nodatainlog mode should be used.
A nodatainlog mode file system is approximately 50 percent slower than a standard mode
VxFS file system for synchronous writes. Other operations are not affected.
blkclear
The blkclear mode is used in increased data security environments. The blkclear mode
guarantees that uninitialized storage never appears in files. The increased integrity is
provided by clearing extents on disk when they are allocated within a file. Extending writes
are not affected by this mode. A blkclear mode file system is approximately 10 percent
slower than a standard mode VxFS file system, depending on the workload.
mincache
The mincache mode has five suboptions:
• mincache=closesync
• mincache=direct
• mincache=dsync
• mincache=unbuffered
• mincache=tmpcache
The mincache=closesync mode is useful in desktop environments where users are likely to
shut off the power on the machine without halting it first. In this mode, any changes to the file
are flushed to disk when the file is closed.
To improve performance, most file systems do not synchronously update data and inode
changes to disk. If the system crashes, files that have been updated within the past minute
are in danger of losing data. With the mincache=closesync mode, if the system crashes or is