Some Linux filesystems don't support-o sync and -o dirsync (the ext2, ext3, fat and vfat filesystems do support synchronous updates (a la BSD) when mounted with the sync option).source
Note:source
It should be remembered that not every file system supports all the parameters.
For example, the sync option today the only supported file systems are ext2, ext3, fat, vfat and ufs.
FILESYSTEM-INDEPENDENT MOUNT OPTIONS
Some of these options are only useful when they appear in the /etc/fstab file.
Some of these options could be enabled or disabled by default in the system kernel. To check the current setting
see the options in /proc/mounts. Note that filesystems also have per-filesystem specific default mount options (see
for example tune2fs -l output for extN filesystems).
The following options apply to any filesystem that is being mounted (but not every filesystem actually honors them –
e.g., the sync option today has an effect only for ext2, ext3, fat, vfat and ufs):
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