Where to start?

[Oliver Fromme]

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

-- 
Oliver Fromme,  secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
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