diff options
| -rw-r--r-- | man/man8/zfs.8 | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/man/man8/zfs.8 b/man/man8/zfs.8 index 57f0b1ba1..fd612afd3 100644 --- a/man/man8/zfs.8 +++ b/man/man8/zfs.8 @@ -1176,11 +1176,33 @@ Controls whether regular files should be scanned for viruses when a file is open .ne 2 .mk .na -\fB\fBxattr\fR=\fBon\fR | \fBoff\fR\fR +\fB\fBxattr\fR=\fBon\fR | \fBoff\fR | \fBsa\fR\fR .ad .sp .6 .RS 4n -Controls whether extended attributes are enabled for this file system. The default value is \fBon\fR. +Controls whether extended attributes are enabled for this file system. Two +styles of extended attributes are supported either directory based or system +attribute based. +.sp +The default value of \fBon\fR enables directory based extended attributes. +This style of xattr imposes no practical limit on either the size or number of +xattrs which may be set on a file. Although under Linux the \fBgetxattr\fR(2) +and \fBsetxattr\fR(2) system calls limit the maximum xattr size to 64K. This +is the most compatible style of xattr and it is supported by the majority of +ZFS implementations. +.sp +System attribute based xattrs may be enabled by setting the value to \fBsa\fR. +The key advantage of this type of xattr is improved performance. Storing +xattrs as system attributes significantly decreases the amount of disk IO +required. Up to 64K of xattr data may be stored per file in the space reserved +for system attributes. If there is not enough space available for an xattr then +it will be automatically written as a directory based xattr. System attribute +based xattrs are not accessable on platforms which do not support the +\fBxattr=sa\fR feature. +.sp +The use of system attribute based xattrs is strongly encouraged for users of +SELinux or Posix ACLs. Both of these features heavily rely of xattrs and +benefit significantly from the reduced xattr access time. .RE .sp |