Re: [gentoo-user] udev and usb stick/hdd

[Alan McKinnon <alan@linuxholdings.co.za>]

On Monday 23 July 2007, maxim wexler wrote:
> > Which will destroy your flash device in as little as
> > a couple of months
> > (voice of experience here), and it probably the
> > reason the option was
> > removed.
>
> Ulp! Here's my line from fstab:
>
> /dev/sdb1       /usb    auto
> noauto,user,rw,exec,sync        0 0
>
> Copied from a forum somewhere. For use of my mp3
> player and digi-camera, both formatted vfat. Does
> 'noauto' cancel 'sync'? This way un/mounting must be
> done manually. Does that spare me?

No. read 'man mount'

In a nutshell, noauto means the device will not be automativcally 
mounted at boot time when the init script runs.
sync is a different beast - it means that "All I/O to the file system 
should be done synchronously." That means that when the kernel say to 
write to the device, it does get written, and not cached somewhere. 
Caching it and returning the correct result to indicate that the write 
was completed would be of course 'async'

> I haven't noticed any problems yet. Are you saying
> that the damage is incremental, that it accumulates
> until a certain point is reached and the device is
> kaput?

It's only a matter of time and relates to how flash devices work. After 
many many writes to the same storage cell, it degrades. The good ones 
are rated to about 100,000 writes per cell. The cheap and nasty ones 
can be as low as 10,000 writes. You would be amazed how quickly 50,000 
writes can happen to the same cell when used as swap for example

This is a known issue with flash devices. The correct solution is to 
ONLY write to the device once you are ready to unmount it. Treat it 
much like a CD and you'll be OK

alan

-- 
Optimists say the glass is half full,
Pessimists say the glass is half empty,
Developers say wtf is the glass twice as big as it needs to be?

Alan McKinnon
alan at linuxholdings dot co dot za
+27 82, double three seven, one nine three five
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