On 5/9/07, Nick Holland <nick@holland-consulting.net> wrote:
quoted text
>
>
> If it was not obvious from my comments, I love softdeps.  I have a
> siteXX.tgz file which does a few simple things, one of which is to
> change all mount points to use softdeps.  One really does have to
> hunt a bit for relevant reasons not to use it.  About the only
> place I can think of where I deliberately don't use it is on an
> e-mail archive system on the filled partitions which are mounted
> read-only.
>
> I can't tell you how many times I have forgot to install my siteXX
> file, started loading up /usr/src, and realized, "Dang, obviously
> no softdeps".  At which point, I stop the checkout, fix the
> problem, reboot, and try again.  Yes, the performance difference
> is that obvious, and it is faster to reboot than it is to wait it
> out.
>

I'm still curious about the issue of using softdep's when you have a
raid card with write-cache (and battery)... I thought I'd do a simple
test unpacking the ports.tar.gz with softdeps disabled/enabled, to
see for myself.

Without softdep enabled, I have the following:

george@skolem# time tar xzf ports.tar.gz
0.970u 2.120s 1:00.62 5.0%      0+0k 9821+210784io 6pf+0w
george@skolem# time rm -r ports
0.160u 1.390s 1:01.65 2.5%      0+0k 14994+126181io 17pf+0w

About a minute to unpack and another minute to remove.


With softdep enabled, I have the following:

george@skolem# time tar xzf ports.tar.gz
1.270u 2.100s 0:45.62 7.3%      0+0k 9874+66318io 59pf+0w
george@skolem# time rm -r ports
0.210u 1.230s 0:14.59 9.8%      0+0k 15741+22055io 17pf+0w

45 seconds to unpack and 15 seconds to remove.

(I've repeated this a few times each way, and I always have
roughly the same results.)

With softdep enabled, there was more cpu time, but a noticeable
decrease in total time.

So, fair to say that even with raid+write-cache+battery that
softdep's are beneficial (in terms of less disk time)?
I'm more interested in maintaining disk-consistency, and with
this setup, it looks like softdeps will still help with that also.


Thanks again for all the info!

-George