Using an SSD "disk" for /

[Jeremy Chadwick]

On Thu, Nov 04, 2010 at 03:29:22PM +0100, Oliver Fromme wrote:
> Jeremy Chadwick wrote:
>  > As for the performance: it's something you'll have to see for yourself.
>  > The performance is outright amazing when it comes to administrative
>  > tasks (OS installation, newfs, massive copies of data to/from the SSD,
>  > updating /usr/src and /usr/ports, etc.).  Try a build/install world or
>  > kernel sometime on an SSD and watch your terminal.  You'll be pretty
>  > impressed.
> 
> What kind of tuning do you apply to those file systems?
> 
> I'm asking because I can't really reproduce those results.
> On a machine with plenty of RAM I've created memory disks
> for obj and src, which should at least be as fast (probably
> even faster) than an SSD.  Buildworld was somewhat faster,
> compared to standard (well-tuned) UFS+SU filesystems on a
> fast SATA HDD, but not _that_ much faster.  In fact the
> difference was small enough that I stopped using memory
> disks and returned to using UFS+SU+noatime (and a few other
> tuning options) on a HDD.
> 
> So, if you experience a _dramatic_ speed-up when using SSDs
> for buildworld, I would really very much like to know why
> this is the case, and what kind of tuning you performed.

Literally: absolutely no tuning.  I treat the SSD the exact same as I
would a standard mechanical HDD: install FreeBSD on it, and that's that.

I imagine the performance difference greatly depends on what SSD you're
actually using.  Again, the Intel drives have the highest IOPS out there
(at least in the consumer-grade market), and I can't justify the cost of
an SLC-based drive, so I stick to MLC.

Possibly you and I have different interpretation of what "dramatic"
means?  :-)  My opinion is that cutting 6-7 full minutes off a
buildworld is pretty dramatic.

-- 
| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |