newfs on a SSD

[Roland Smith]

On Fri, May 11, 2012 at 09:01:33AM +0200, Christer Solskogen wrote:
> After years of waiting for a decent price on one of these I finally
> got one. The questions is, which options should I use on a SSD that
> will be / on my system. I see that newfs supports TRIM, so that will
> be turned on, but should I use journaling? gjournal? softupdates? soft
> updates journaling? I'm confused :)

Enabling TRIM with the '-t' option for newfs sounds like a good idea. Assuming
the underlaying device supports it. You can check that with the 'camcontrol
identify' command, assuming you're using the ada(4) driver.

OCZ has a page with tips for Linux. Some would apply to FreeBSD as well;
http://www.ocztechnologyforum.com/forum/showthread.php?54379-Linux-Tips-tweaks-and-alignment&highlight=linux

Aligning the partitions with the Erase Block Size is important. See: 
https://wiki.archlinux.org/index.php/Solid_State_Drives

One thing to keep in mind is to mount the filesystems you make on the SSD with
the "noatime" option. This to avoid a lot of unnecessary writes.

Some of the newfs parameters like blocks per cilinder group don't seem to make
much sense for an SSD. Since the controller of the SSD already does all kinds
of things to emulate a harddisk, I'm not sure if it makes much sense to tune
the filesystem's parameters much.

As for softupdates (journaled of not): try it and let us know if you see
differences, especially in write performance. :-)

The FreeBSD foundation has awarded a grant to port a special Flash filesystem
and tools to FreeBSD:
http://freebsdfoundation.blogspot.com/2012/03/new-project-nand-flash-support.html
It might be worthwhile to keep that in mind for the future. 

What I would certainly recommend is that you make a daily automated backup
(may I suggest calling rsync from cron at night?) of the SSD's filesystem to
an actual HDD, just to be sure.

Roland
-- 
R.F.Smith                                   http://rsmith.home.xs4all.nl/
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