Warren Block wblock at wonkity.com
Mon Jul 9 03:30:10 UTC 2012

On Sun, 8 Jul 2012, Graham Bentley wrote:

> Hi I have put together a little experimental FreebSD 9.0
> box which comprises of ;
> http://www.cartft.com/catalog/il/934
> http://www.overclockers.co.uk/showproduct.php?prodid=HS-023-ZA
> 2GB RAM and a Sandisk SDSA3BD-054G 8GB SSD
> The idea is a silent system I can tinker on - nothing serious. I chose the 
> guided install and accepted the default partition / fs layout. I thought the 
> things where running a bit slow and changed from 'native' in the BIOS to 
> 'legacy' SATA and things seem a bit quicker now however I am wondering if I 
> am getting the bext out of the SDD? I have read a little about 'aligning' and 
> 4k sectors I think? If its running ok should I leave as is? Or do you have 
> tunning advice for me?

The default install of 9.0-RELEASE does not align to 4k sectors.
Depending on the SSD, this might cost a little or a lot of performance. 
The example gpart commands I posted in the "Format a USB flash drive" 
thread create aligned partitions:


1. SSDs don't necessarily use 4k blocks, some use larger ones. 
Starting the first filesystem partition at 1M works for most of the 
common values.

2. As Bruce Cran pointed out, TRIM can be enabled with UFS.  But make 
sure the SSD supports it first.

3. Swap is tricky with small drives, even trickier if you want to use 
TRIM.  Swap files can be used, and then you get TRIM, but see 
http://www.freebsd.org/cgi/query-pr.cgi?pr=bin/168544 for a way to 
dismount that swap file before shutdown and an annoying panic.

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