Google SoC idea

Pawel Jakub Dawidek pjd at
Tue Jun 7 19:40:13 GMT 2005

On Mon, Jun 06, 2005 at 06:11:23PM +0200, Ivan Voras wrote:
+> I have an idea that I could implement through Google's "Summer of Code" 
+> project, but as I have little experience with stuff it involves (kernel 
+> programming / disks / filesystem optimization), so I expect any answer 
+> from "It won't work" or "It's useless" to "It can't be done".  :)
+> The idea is this: to implement sort of GEOM-layer disk data journaling 
+> system. I imagine it to be a GEOM class using two "lower-level" devices: 
+> one for data and one for the "journal" (this way, the journal device can 
+> be on a fast and small disk). Such journaled device could be used to 
+> host any filesystem, probably mounted with synchronoues-access, and it 
+> will result in faster write access by keeping the writes sequential in 
+> the "journal" device. Journal information will be commited to the data 
+> disk periodically by a separate log-writer thread, or when it gets full. 
+> The "data disk" will be consistent so it can be used without it's 
+> "journal" part (after a clean disconnect/rebuild) if needed. At the 
+> worst case, I think this will help performance in cases when there's a 
+> burst of write activity followed by a period of IO idleness.
+> I've made the above idea more-or-less from my head in one afternoon, so 
+> it's perfectly possible that I'm missing some vital point or that it's 
+> complete nonsense :)
+> Does it make sense to do it this way? Is it worth applying for the SoC?

Not sure. Basically this is simlar what softupdate does, I think.
From another point of view softupdates are only available for UFS.
You probably wants to hear scottl and phk opinions (CCed).

Pawel Jakub Dawidek             
pjd at                 
FreeBSD committer                         Am I Evil? Yes, I Am!
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