Where to start?

[Eric Anderson]

On 01/25/07 04:57, Oliver Fromme wrote:
> Mike Silbersack wrote:
>  > Eric Anderson wrote:
>  > 
>  > > Why not disable swap, use the swap partition as the new journaling device, 
>  > > and then enable vn-backed swap for the system?
>  > 
>  > I wouldn't want to disable swap,
> 
> Eric didn't say to disable swap permanently.  Only disable
> the existing swap partition (use swapoff(8)) and then use
> it for the journal.  Then create a swap file in an existing
> file system and use that one for swapping.
> 
>  > but if I could use some percentage of swap, then it would rock.
> 
> That would be possible, too, of course.  Disable swapping
> temporarily with swapoff(8), then shrink the swap partition
> with bsdlabel(8) and create a new partition in the free
> space.  Then resume swapping with swapon(8) on the swap
> partition (which is now smaller), and use the new partition
> for the journal.  If swap is now too small, you can still
> create an additional swap file in an existing file system,
> of course.
> 
> However, note that the journal requires a certain minimum
> size which depends on the thoughput of data on that file
> system.  I guess that half of the swap partition would be
> too small in many common cases.
> 
> Unfortunately, FreeBSD doesn't have shrinkfs(8), which
> would be extremely useful to add space for a journal to
> an existing disk (among other things).  Maybe this is
> something that should be added to the ideas web page.
> 
> Best regards
>    Oliver
> 

I think you could also reduce the journaling sync time for gjournal to 
reduce the needed journal size, but pjd@ would be best to answer that one.

Eric