the sync command controls the synchronization of cache nothing more.
essentially it can force your write cache to push down to the block
device it can also be used to clear your cache in ram.


On Tue, Jul 15, 2014 at 2:02 PM, ToddAndMargo <[log in to unmask]> wrote:
> On 07/15/2014 10:52 AM, Patrick J. LoPresti wrote:
>>
>> On Tue, Jul 15, 2014 at 10:44 AM, Paul Robert Marino
>> <[log in to unmask]> wrote:
>>>
>>> I have a question about your test did you unmount the stick between
>>> runs of rsync. if not you may have already had all of the information
>>> about the filesystem cached in memory instead of having to search the
>>> FAT table for information. this could have a huge effect on the speed
>>> of an update.
>>
>>
>> Good suggestion, although I would recommend instead:
>>
>>      /sbin/sysctl -w vm.drop_caches=3
>>
>> This will flush the page cache completely and avoid the need to
>> unmount+remount. It will also drop cached data for all mounted
>> partitions (in this case, both the source and the destination of the
>> rsync), which is usually what you want before performing any benchmark
>> involving the file system.
>>
>>   - Pat
>>
>
> Who would this differ from the "sync" command?
>
> Options="-rv --delete --modify-window=1 --times --inplace --copy-links "
> rsync ${Options} $MyCDsSource/Linux  $MyCDsTarget/.; sync; sync
>
> --