cvs commit: src/sys/kern kern_shutdown.c

[Scott Long]

Johan Pettersson wrote:

> On Thu, 22 Jul 2004 07:44:45 -0600
> Scott Long <scottl at samsco.org> wrote:
> 
> 
>>Peter Jeremy wrote:
>>
>>>On Wed, 2004-Jul-21 15:57:30 -0600, Scott Long wrote:
>>>
>>>
>>>>Implementing a journalling filesystem would be a much more
>>>
>>>beneficial>use of time here.
>>>
>>>
>>>You still wind up with unwritten data in RAM, just less of it.
>>>
>>>How much effort would be required to add journalling to UFS or UFS2?
>>>How big a gain does journalling give you over soft-updates?
>>>
>>
>>That's a very good question.  A group at RPI has been working on it
>>for some time, but I'm not sure how close they are to having it done. 
>>If you look in the commercial world, Apple, Sun, and Wasabi/NetBSD
>>have all done it successfully (Wasabi's isn't open source, btw).  My
>>guess is that it would take about 4-5 months to get it going, and then
>>at least 8-12 months to ensure that there are no bugs and to tune
>>performance. Certainly not impossible, but not something that would be
>>production quality on short notice.  I think that you would also have
>>to make it othogonal to softupdates.
>>
>>The gain that you get is that your filesystem recovery time drops
>>tremendously.   You also have a much better chance of all of the
>>metadata being on the disk and recoverable.  Furthermore, it opens the
>>door for data+metadata journalling for even more protection (at a
>>large cost to speed and/or buffer-cache pressure, of course).
>>
>>Scott
> 
> 
> Isn't there ongoing work to port XFS to FreeBSD?

There was, but it seems to have stalled due to lack of time by the
person who was doing it.  Also, the XFS port would have GPL licensing
issues and therefor isn't suitable for everyone.

Scott