Re: rsync 10 times slower in Etch than in Sarge!
on Fri, Jan 18, 2008 at 12:16:28PM -0500, Douglas A. Tutty wrote:
>> > Why issue a 'sync' instead of just unmounting and waiting until the
>> > thing stops flashing?
On Fri, Jan 18, 2008 at 09:24:22AM -0900, Ken Irving <fnkci@uaf.edu> was heard
to say:
>> sync blocks, so you can tell from the command line when the job is done.
Daniel Burrows <dburrows@debian.org> writes:
> So does umount. (I see you said that below, but I wanted to underline
> it again; it looks like Rudolfo overlooked it) After "umount"
> completes, it's safe to remove the stick.
Rodolfo:
>> I didn't overlook this, but:
>>
>> 1) in my experience, some time ago I used to extract the pendrive after
>> `umount' completes and the device often got corrupted. When I asked this
>> list for help to recover it, someone suggested to apply the `sync' option
>> to the mount option: since then I put that option in my fstab, until this
>> thread advised not to do so;
Daniel Burrows <dburrows@debian.org> writes:
> I've been using Linux for 10 years, and I've always, always, always
> heard that "umount" had a side effect of flushing dirty buffers to disk
> and syncing the filesystem.
>
>
> But I did a little research before I replied, and I came up with some
> surprising information. [...]
Rodolfo:
>> 2) I measured the time, and it seems to me that the `sync' command takes a
>> little longer than `umount' to stop.
Daniel:
> I don't know for sure, but this could be because "sync" flushes the
> write buffers on all devices, not just the one you're pulling out.
Thanks for taking care of the important matter.
Then I presume that if I use both issues, i.e. first do `sync' and then
`umount', I should feel quite safe: is that right? I did so some times now
(with no `sync' option left in my fstab) and nothing bad has happened up to
now.
Bye
Rodolfo
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