Re: ReiserFS / 2.4.6 / Data Corruption

[Andrew Morton]

Hans Reiser wrote:
> 
> Andrew, can you do this such that there is no disruption of our
> disk format, and make a mount option
> out of it, and probably we should use this patch....

I'll defer to Chris :)

There's no disruption to disk format - it just simulates
the user typing `sync' at the right time.  I think the
concept is sound, and I'm sure Chris can find a more efficient
way...

> After you make a mount option out of it, grev will benchmark
> it for us using the usual suite of benchmarks.
> 

Ordered-data is a funny thing.  Under heavy loads it tends
to make a significant throughput difference - on ext3 it 
almost halves throughput wrt writeback mode.

But this by no means indicates that writes are half as slow;
what happens is that metadata-intensive workloads fill the
journal up quickly, so the `sync' happens more frequently.
Under normal workloads, or less metadata-intense workloads
the difference is very small.

During testing of that little patch I noted that the 
disk went crunch every thirty seconds or so, which is good.
Presumably the reiserfs journal is larger, or more space-efficient.

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