New option -disk_dev_ino

xorriso/xorriso.1

@@ -667,6 +667,20 @@ Enable or disable processing of xattr attributes in user namespace.
 If enabled, then xorriso will handle xattr similar to ACL.
 See also options -getfattr, -setfattr and above paragraph about xattr.
 .TP
+\fB\-disk_dev_ino\fR "on"|"off"
+Enable or disable processing of recorded file identification numbers
+(dev_t and ino_t). They are eventually stored as xattr "isofs.di" and allow
+to substantially accelerate file comparison:
+.br
+If device numbers and inode numbers of the disk filesystems are persistent
+and if no irregular alterations of timestamps or system clock happen,
+then potential content changes can be detected without reading that content.
+File content change is assumed if any of mtime, ctime, device number or inode
+number have changed.
+.br
+The speed advantage appears only if the loaded session was produced with
+-disk_dev_ino "on" too.
+.TP
 \fB\-rom_toc_scan\fR "on"|"off"[:"emul_on"|"emul_off"]
 Read-only drives do not tell the actual media type but show any media as
 ROM (e.g. as DVD-ROM). The session history of MMC multi-session media might
@@ -3115,7 +3129,8 @@ the old one.
 .br
 This makes sense if the full backup leaves substantial remaining capacity
 on media and if the expected changes are much smaller than the full backup.
-An update run will probably save no time but last longer than a full backup.
+An update run will probably save no time but last longer than a full backup,
+unless option -disk_dev_ino "on" is used.
 .br 
 With \fBmount\fR option \fB-o "sbsector="\fR on Linux resp. \fB-s\fR on FreeBSD
 it is possible to access the session trees which represent the older backup