Veritas File System 5.1 SP1 Administrator"s Guide (5900-1499, April 2011)

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.

The blkclear mode

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. This mode does not affect extending writes. A blkclear mode file system

is approximately 10 percent slower than a standard mode VxFS file system,

depending on the workload.

The mincache mode

The mincache mode has the following 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 open files can lose data. A

mincache=closesync mode file system could be approximately 15 percent slower

than a standard mode VxFS file system, depending on the workload.

The following describes where to use the mincache modes:

VxFS performance: creating, mounting, and tuning file systems

Mounting a VxFS file system