.B \-L
.I volume_label
] [
+.B \-\-pack\-bitmap
+] [
.B \-v
]
.I device
.PP
.SH OPTIONS
.TP
-.BI \-b " boundary_alignment"
-Specify the alignment for FAT and start of cluster.
-Boundary alignment can be specified in m/M for megabytes
-and k/K for kilobytes. It should be a power of two.
-Some media like sdcard need this.
+.BR \-b ", " \-\-boundary\-align =\fIalignment\fR
+Specifies the alignment for the FAT and the start of the cluster heap.
+The \fIalignment\fR argument is specified in bytes or may be specified with
+\fBm\fR/\fBM\fR suffix for mebibytes or \fBk\fR/\fBK\fR suffix for kibibytes
+and should be a power of two.
+Some media like SD cards need this for optimal performance and endurance,
+in which case \fIalignment\fR should be set to half of the card's native
+boundary unit size.
+If the card's native boundary unit size is not known, refer to the following
+table of boundary unit sizes recommended by the SD Card Association.
+.\" source: SD Specifications Part 2: File System Specification Version 3.00
+.TS
+center;
+cb1s6cbcb,nnnn.
+Card Capacity Range Cluster Size Boundary Unit
+_
+ \[<=]8 MiB 8 KiB 8 KiB
+>8 MiB \[<=]64 MiB 16 KiB 16 KiB
+>64 MiB \[<=]256 MiB 16 KiB 32 KiB
+>256 MiB \[<=]1 GiB 16 KiB 64 KiB
+>1 GiB \[<=]2 GiB 32 KiB 64 KiB
+>2 GiB \[<=]32 GiB 32 KiB 4 MiB
+>32 GiB \[<=]128 GiB 128 KiB 16 MiB
+>128 GiB \[<=]512 GiB 256 KiB 32 MiB
+>512 GiB \[<=]2 TiB 512 KiB 64 MiB
+.TE
.TP
-.BI \-c " cluster_size"
-Specify the cluster size. Cluster size can be specified in m/M for megabytes
-and k/K for kilobytes.
+.BR \-c ", " \-\-cluster\-size =\fIsize\fR
+Specifies the cluster size of the exFAT file system.
+The \fIsize\fR argument is specified in bytes or may be specified with
+\fBm\fR/\fBM\fR suffix for mebibytes or \fBk\fR/\fBK\fR suffix for kibibytes
+and must be a power of two.
.TP
-.BI \-f
-Performs a full format. This zeros the entire disk device while
-creating the exFAT filesystem.
+.BR \-f ", " \-\-full\-format
+Performs a full format.
+This zeros the entire disk device while creating the exFAT filesystem.
.TP
-.BI \-h
+.BR \-h ", " \-\-help
Prints the help and exit.
.TP
-.BI \-L " volume_label"
-Specifies the volume label associated with the exFAT filesystem.
+.BR \-L ", " \-\-volume\-label =\fIlabel\fR
+Specifies the volume label to be associated with the exFAT filesystem.
+.TP
+.B \-\-pack\-bitmap
+Attempts to relocate the exFAT allocation bitmap so that it ends at the
+alignment boundary immediately following the FAT rather than beginning at that
+boundary.
+This strictly violates the SD card specification but may improve performance
+and endurance on SD cards and other flash media not designed for use with exFAT
+by allowing file-system metadata updates to touch fewer flash allocation units.
+Furthermore, many SD cards and other flash devices specially optimize the
+allocation unit where the FAT resides so as to support tiny writes with reduced
+write amplification but expect only larger writes in subsequent allocation
+units \[em] where the exFAT bitmap would be placed by default.
+Specifying \fB\-\-pack\-bitmap\fR attempts to avoid the potential problems
+associated with issuing many small writes to the bitmap by making it share an
+allocation unit with the FAT.
+If there is insufficient space for the bitmap there, then this option will have
+no effect, and the bitmap will be aligned at the boundary as by default.
.TP
-.BI \-v
+.BR \-v ", " \-\-verbose
Prints verbose debugging information while creating the exFAT filesystem.
.TP
-.B \-V
+.BR \-V ", " \-\-version
Prints the version number and exits.
.SH SEE ALSO
.BR mkfs (8),
projects / sven / exfatprogs.git / blobdiff