Re: [MLUG - DISCUSSION] "missing" files after hard crash or power failure

[Stephen Montgomery-Smith <EMAIL:PROTECTED>]

Mark Rages wrote:
> On 4/2/07, George Robb <EMAIL:PROTECTED> wrote:
> > There is a package for playing with the cache / drive parameters in
> > general...  hdparm
> >
> > http://freshmeat.net/projects/hdparm/
> >
> > http://www.linuxdevcenter.com/pub/a/linux/2000/06/29/hdparm.html
> >
> > A simple hdparm /dev/<your drive here (not partition)>  will tell the
> > current parameters.
> >
> > Good point that if there is a large cache on the drives or if they
> > are on a RAID controller there could be some serious data floating in
> > cache.
> >
> > ;)
>
> Does sync() cause the data to be written?  I'm guessing no, since the
> man page says:
>
>     According  to the standard specification (e.g., SVID), sync() 
> schedules
>     the writes, but may return before the actual writing is done.  
> However,
>     since  version  1.3.20  Linux does actually wait.  (This still 
> does not
>     guarantee data integrity: modern disks have large caches.)
>
> Regards,
> Mark
> EMAIL:PROTECTED

Yes you are correct.  Sync is not a sure fire solution.

My situation was this.  I had a file which was overwritten every five 
minutes or so - this was meant to keep track of some internal condition 
in a program so that it could be restarted if it was stopped for some 
reason.  When I had a system crash, this file was typically a day out of 
date (which meant I had lost about a day's work).  Repeated 'sync's 
didn't help at all.


Stephen


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