Help review the FAQ

[Bas Smeelen]

On 11/26/12 17:25, Jakub Lach wrote:
> Thanks!
>
> Regarding FAQ, some info about journalling should  be added to
> "Chapter 9 Disks, File Systems, and Boot Loaders", especially now,
> when SU+J is default.

Add to FAQ 9.4 Which partitions can safely use Soft Updates? I have 
heard that Soft Updates on / can cause problems.

Journaled Soft Updates (SU+J) is now default on FreeBSD 9.x-RELEASE 
installs.
This feature keeps a journal on soft updates which avoids a background 
filesystem check and speeds up a filesystem check during boot to a few 
seconds or less.
For history and technical details see:
http://jeffr-tech.livejournal.com/22716.html
and
http://www.*bsdcan*.org/2010/schedule/attachments/141_suj-slides.pdf

This can also be enabled/disabled with tunefs -j enable | disable
For more information see man 8 tunefs

----------------

New FAQ 9.28 I have heard about TRIM for Solid State Drives (SSD), is it 
supported by FreeBSD?

The TRIM filesystem flag is very useful for devices that use 
flash-memory (SSD for instance) and support the BIO_DELETE command.
This flag is not enabled by default and can be enabled/disabled with 
tunefs -t enable | disable
For more information see man 8 tunefs
      -t enable | disable
              Turn on/off the TRIM enable flag.  If enabled, and if the 
under-
              lying device supports the BIO_DELETE command, the file system
              will send a delete request to the underlying device for each
              freed block.  The trim enable flag is typically set when the
              underlying device uses flash-memory as the device can use the
              delete command to pre-zero or at least avoid copying 
blocks that
              have been deleted.

Important when using tunefs:
      This utility does not work on active file systems.  To change the root
      file system, the system must be rebooted after the file system is 
tuned.

FIlesystems have to be mounted read-only or not mounted at all