Messages in this thread |  | | | Date | Wed, 2 Sep 2009 22:12:10 +0200 | | From | Pavel Machek <> | | Subject | Re: [testcase] test your fs/storage stack (was Re: [patch] ext2/3: document conditions when reliable operation is possible) |
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>>> people aren't objecting to better documentation, they are objecting to >>> misleading documentation. >>> >> Actually Ric is. He's trying hard to make RAID5 look better than it >> really is. > > I object to misleading and dangerous documentation that you have > proposed. I spend a lot of time working in data integrity, talking and > writing about it so I care deeply that we don't misinform people.
Yes, truth is dangerous. To vendors selling crap products.
> In this thread, I put out a draft that is accurate several times and you > have failed to respond to it.
Accurate as in 'has 0 information content' :-(.
> The big picture that you don't agree with is: > > (1) RAID (specifically MD RAID) will dramatically improve data integrity > for real users. This is not a statement of opinion, this is a statement > of fact that has been shown to be true in large scale deployments with > commodity hardware.
It is also completely irrelevant.
> (2) RAID5 protects you against a single failure and your test case > purposely injects a double failure.
Most people would be surprised that press of reset button is 'failure' in this context.
> (4) Data loss occurs in non-journalling file systems and journalling > file systems when you suffer double failures or hot unplug storage, > especially inexpensive FLASH parts.
It does not happen on inexpensive DISK parts, so people do not expect that and it is worth pointing out. Pavel
-- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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