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

["shawn parker" <EMAIL:PROTECTED>]

both servers are dell poweredges using perc raid controllers. like i
said previously, the /home partition is local but the /arcgis is
stored on the san (dell emc).

i don't see how local drive cache would be an issue at least with
/arcgis. i think /arcgis is a raid 10 lun; i'll have to check
navisphere.

i'm unsure how the emc san works in regards to "physical" disk cache;
i'll have to do some research on that. to linux, it is just another
patition (/emcpowerr1) mounted to /arcgis.

/home resides on a local raid 1.

plus, according to our oracle dba and our gis specialist, sde isn't
that active of an application. i don't know why linux would cache this
over anything else running on the server. a dozen or so san mounts
running gis software and oracle databases and this is the only
anomaly.


thanks for the information and ideas!


On 4/2/07, Mark Rages <EMAIL:PROTECTED> 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
> --
> Most of the time,
> for most of the world,
> no matter how hard people work at it,
> nothing of any significance happens.
>      -- Weinberg's Law
>
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