9.0 on SSD

Wojciech Puchar wojtek at wojtek.tensor.gdynia.pl
Sat Jun 2 16:28:38 UTC 2012

>> filesystem which resides on the SSD. Is it good, bad or irrelevant for
>> the SSD ?
> Mostly irrelevant, I think.  I've been using just ordinary soft updates as 
> there is bug fixing going on with SU+J.  fsck on the SSD is very fast anyway, 
> so SU+J is needed less.  And there's a little less writing because there is 
> no journal.  But then, I've left atime on, too.
> _______________________________________________

i have FreeBSD 9 and SSD (OCZ Agility 3 "60GB")

DO NOT use any kind of journalling - this increase writes and wear, while 
fsck takes <10 seconds for me.

do use -t option for newfs.

make sure your FS partition is aligned to 4 kilobytes. All these web 
advices about aligning to 1MB is classic pure nonsense (most often used 
NTFS aligns to 4kB anyway).

run without swap or make pseudo-dynamic swap with mdconfig ;)

My config:

1) no MSDOS partitions (slices). not needed no matter if it is SSD or not. 
unless you run windoze too.

2) single partition for FreeBSD, SSD are not huge and wasting space for 
partitions isn't smart.


# /dev/ada0:
8 partitions:
#          size     offset    fstype   [fsize bsize bps/cpg]
   a:  117231408          0    4.2BSD        0     0     0
   c:  117231408          0    unused        0     0     # "raw" part, don't edit

3) newfs -m 0 -i 16384 -b 8192 -f 1024 -U -t /dev/ada0a
or similar settings. maybe you can run with less inodes (in my case i've 
got 3.6M inodes).

for rare case swapping i do in /etc/rc.local
echo creating swapfile
/bin/rm -f /swapfile.tmp
dd if=/dev/zero of=/swapfile.tmp bs=8m seek=1k count=0
/sbin/mdconfig -a -t vnode -u 0 -f /swapfile.tmp || /bin/sh
/bin/rm -f /swapfile.tmp
/sbin/swapctl -a /dev/md0

and in /etc/rc.shutdown.local

echo removing swapfile
/sbin/swapctl -d /dev/md0
/sbin/mdconfig -d -u 0

this will allocate 8GB file with holes, space would be allocated when 
actually needed, and deallocated on shutdown.

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