On Thu 2008-03-13 12:03:03, Daniel Phillips wrote:
quoted text
> On Thursday 13 March 2008 12:50, David Newall wrote:
> > Daniel Phillips wrote:
> > > The period where you cannot access the data is downtime.  If your script
> > > just does a cp from a disk array to the ram device you cannot just read
> > > from the backing store in that period because you will need to fail over
> > > to the ramdisk at some point, and you cannot just read from the ramdisk
> > > because it is not populated yet.
> > 
> > Wouldn't a raid-1 set comprising disk + ramdisk do that with no downtime?
> 
> In raid1, write completion has to wait for write completion on all
> mirror members, so writes run at disk speed.  Reads run at ramdisk
> speed, so your proposal sounds useful, but ramback aims for high
> write performance as well.

raid1 + kflushd tweak?

special raid1 mode that signals completion when it hits _one_ of the
drives, and does sync when the slower drive is idle?
							Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
--
unsubscribe notice
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/