Would it really be that much slower to have a journal of RAID 5 writes?

On Fri, 2005-11-18 at 15:05 +0100, Jure Pečar wrote:
> Hi all,
> 
> Currently zfs is a major news in the storage area. It is very interesting to 
> read various details about it on varios blogs of Sun employees. Among the 
> more interesting I found was this:
> 
> http://blogs.sun.com/roller/page/bonwick?entry=raid_z
> 
> The point the guy makes is that it is impossible to atomically both write 
> data and update parity, which leaves a window of crash that would silently 
> leave on-disk data+paritiy in an inconsistent state. Then he mentions that 
> there are software only workarounds for that but that they are very very slow.
> 
> It's interesting that my expirience with veritas raid5 for example is just 
> that: slow to the point of being unuseable. Now, I'm wondering what kind of 
> magic does linux md raid5 does, since its write performance is quite good? 
> Or, does it actually do something regarding this? :)
> 
> Niel?
> 

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