Help review the FAQ

Bas Smeelen b.smeelen at
Mon Nov 26 20:53:27 UTC 2012

On 11/26/12 21:27, Bas Smeelen wrote:
> 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.

Please also add:
SU+J does not work (yet) with dump on a live filesystem i.e. use snapshot.
If you want to use snapshot (dump -L) then disable the soft updates 
journal for that filesystem

> 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:
> 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

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