Re: Linux 2.6.29

Benny Halevy
2009-03-25T09:35:37Z

On Mar. 24, 2009, 21:55 +0200, Jeff Garzik <jeff@garzik.org> wrote:
> Linus Torvalds wrote:
>> But I really don't understand filesystem people who think that "fsck" is
>> the important part, regardless of whether the data is valid or not. That's
>> just stupid and _obviously_ bogus.
>
> I think I can understand that point of view, at least:
>
> More customers complain about hours-long fsck times than they do about
> silent data corruption of non-fsync'd files.
>
>
>> The point is, if you write your metadata earlier (say, every 5 sec) and
>> the real data later (say, every 30 sec), you're actually MORE LIKELY to
>> see corrupt files than if you try to write them together.
>>
>> And if you write your data _first_, you're never going to see corruption
>> at all.
>
> Amen.
>
> And, personal filesystem pet peeve: please encourage proper FLUSH CACHE
> use to give users the data guarantees they deserve. Linux's sync(2) and
> fsync(2) (and fdatasync, etc.) should poke the block layer to guarantee
> a media write.

I completely agree. This also applies to nfsd_sync, by the way.
What's the right place to implement that?
How about sync_blockdev?

Benny

>
> Jeff
>
>
> P.S. Overall, I am thrilled that this ext3/ext4 transition and
> associated slashdotting has spurred debate over filesystem data
> guarantees. This is the kind of discussion that has needed to happen
> for years, IMO.
>
>
>
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Benny Halevy
Software Architect
Panasas, Inc.
bhalevy@panasas.com
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