On Tue, Mar 29, 2005 at 06:13:05PM +0200, Karsten Kruse wrote:
> Michael Graff wrote:
> 
> > Try unplugging it while it's mid-build.  If that works, try it 10 times more 
> > at various points.  If you FS lives, cool.  Mine does not, on i386.
> 
> I guess that your writeback cache is active. In that case softdep can not
> safe you from powerfailure because the disk writes when it's in the mood,
> not when it got the command to write.
> 
> But even in this case a fs with softdep is safer than one without- It
> safes you when you accidently press reset or a kernel-panic occurs (the
> dirty stuff in the writeback cache can be written to disk as long as you
> have power).
> 
> Performance is a bonus, i think the safety alone is worth it.

I've got three out of four (everything but my root / main stuff disk) disks
running with softdeps, and while they DO perform better with softdeps, I've
noticed some drawbacks, such as when (for example) untarring pkgsrc. If I'm
doing it on a softdep'd partition on a nice fast disk (this box is an
XP2700+ with 1GB ram) it'll complete in about 19 seconds - then lag the HELL
out of the machine as it actually goes about doing the real writes. To the
point where it almost feels like it's hardlocked the system. I've had this
happen several times, only on softdep'd filesystems.

- Sean

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