creating SYNC option for all USB devices in hal 0.0.4-10

[Artem Kachitchkine]

Martin Pitt wrote:
> Yes, it is. Depending on the application you use, you'll see a factor
> of about 10 to 100.
> 
> Another fact is that at least the current implementation of sync is
> EVIL for flash devices. I got reports of destroyed flash chips because
> earlier versions of Ubuntu mouted devices as sync by default. But this
> dramatically increases the wearout of certain portions of the flash
> memory (FAT tables and the like), which leads to a greatly reduced
> lifetime. So don't do it if you want to keep your devices for a while.

Many (most?) modern flash devices perform some sort of write leveling:

http://www.sandisk.com/pdf/oem/WPaperWearLevelv1.0.pdf

I also find it curious that Windows still decided to disable write 
caching in XP SP2 by default:

http://www.microsoft.com/whdc/system/pnppwr/hotadd/XPrem-devs.mspx

Perhaps it is not entirely a hardware problem, the OS can also be 
smarter to reduce the wear and the performance hit. This sounds like an 
interesting optimization problem.

-Artem.