On 18/07/12 11:52, Edward Ned Harvey wrote:
From: [email protected] [mailto:[email protected]]
On Behalf Of Andrew Hume
i have two linux servers each of which has the same piece of SAN
attache dto it as a LUN. that is, svra:/dev/sdbd is the same volume
(or more exactly WWN) as svrb:/dev/sdaf.
what i want to do is write something on svra to /dev/sdbd
and then be able to read it on svrb from /dev/sdaf.
in principle this should work, but on Linux the buffer
cache always inserts doubt. how do i reliably probe
/dev/sdaf for new content? there is no filesystem involved;
i am just talking about raw disk blocks.
I see other people have already answered this, regarding no filesystem. But
you might also consider using a clustered filesystem. The whole point of
such a thing is to do precisely this... With a filesystem. I believe the
"standard" option built-into most linuxes nowadays would be gfs. (Not to be
confused with google GFS.
A clustered file system would probably use (i)SCSI reservations (or the
FC equivalent) to ensure a host has exclusive access before updating
meta-data on the shared disk.
Jonathan.
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