Veritas File System 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

VxFS Performance: Creating, Mounting, and Tuning File Systems
Choosing mount Command Options
Chapter 230
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 switched off, only files that are currently open
can lose data. A mincache=closesync mode file system should be approximately 15 percent slower than
a standard mode VxFS file system, depending on the workload.