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Re: ext3 and data=journal bug



Thanks, Andrew.

Most webservers are, in fact, mostly read-only.  But these are more of a 
complete  hosting solution, so they are web/mail/pop/sql servers.  I've run 
about 8 different benchmarking tests, 4 per ordered/journal modes, and 
journal wins out by far.  The times for reads/writes in journal'd mode were 
nearly 1/4th of those in ordered.  

Also, I was testing with the elevator settings at 
read = 16384 and write =  8192

So,  I'm going to push for data=journal if I am positive that the sync bug had 
been fixed.  Any ideas on that?

Thanks alot,

Mark


On Thursday 01 May 2003 12:16 am, Andrew Morton wrote:
> Mark A Basil <mbasil alabanza com> wrote:
> > Greetings all,
> >
> > I have a question regarding the fsync data corruption bug that was
> > introduced in 2.4.20 when using data=journal.  I have patched the 2.4.20
> > kernel with the 3 sync patches available from zip.com.au, and I am
> > wondering if with these patches the "bug" still exists:
> >
> > sync_fs.patch
> > sync_fs-fix.patch
> > sync_fs-fix-2.patch
> >
> > In addition the following two patches have also been applied:
> >
> > ext3-use-after-free.patch
> > ext3-scheduling-storm.patch
>
> That sounds right - it gets you up to 2.4.21-rc1's ext3.
>
> > Also, from what I understand 'data=journal' would be beneficial in cases
> > where data is being written to and read from disks constantly.  Would it
> > be advised to use this data mode in a webserver environment in which
> > there are many virtual hosts(provided the above bug was fixed with the
> > patches)?
>
> Probably not.  data=journal can help in certain specialised workloads where
> there is a lot of O_SYNC/fsync activity.  Mail servers, NFS servers, etc.
>
> > Would the above settings not crush the server?  Those settings are
> > flushing fs metadata about once per second, and data blocks every 600
> > seconds.
>
> Those settings were to address a specific problem wherein an NFS server
> with synchronous exports would keep on filling the ext3 journal and forcing
> lots of blocking writeout.
>
> I'd expect you'll be OK with default journalling mode and default bdflush
> settings.  web servers are almost read-only aren't they?
>
> You should seriously consider mounting with `noatime' - that will
> significantly reduce the filesystem's writeout volume.
>
>
>
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