On Thu, Aug 13, 2009 at 10:25:15PM +0200, Vladimir 'phcoder' Serbinenko wrote: > On Thu, Aug 13, 2009 at 10:05 PM, Robert Millan<r...@aybabtu.com> wrote: > > On Thu, Aug 13, 2009 at 06:04:35PM +0200, Vladimir 'phcoder' Serbinenko > > wrote: > > > > This looks a bit odd (a mask applied to an integer?), but if it's really > > this way, please go ahead with it. > > > It's the so-called skewness. > Let's say you place inodes on addresses (C/H/S) > (0/0/1) and (1/0/1) you first read the metadata at (0/0/1) then you > try to fetch the metadata from (0/1/1). Responding to your request > harddrive moves the head to cylinder number 1 but it takes some time. > Meanwhile the plates have spinned (they are spinning constantly) and > perhaps head is above sector (1/0/10) and you need to wait for > complete rotation to fetch your sector. > If you write inodes at (0/0/1) and (1/0/15) you will need to wait only > for 4 sectors. This is called skewness and was an optimisation > technique in the past. But now OS doesn't know about physical geometry > and so can't do such kind of optimisation. I suppose it's why it's not > used anymore for UFS2. I don't know if FreeBSD variant of UFS1 still > uses this feature.
I see :-) -- Robert Millan The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and how) you may access your data; but nobody's threatening your freedom: we still allow you to remove your data and not access it at all." _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org http://lists.gnu.org/mailman/listinfo/grub-devel
