Re: ext4 features

["Jeff V. Merkey" <jmerkey@wolfmountaingroup.com>]

Arjan van de Ven wrote:

> >  ZFS was already called ,,blatant layering violation''. ;)
> > Yes,that what RAID is for. And if we want checksums in filesystem,
> > that's the best way to utilise them.
> >    
>
>
> Hi,
>
> checksums have a very different purpose than raid.
>
> checksums are great at detecting corruption. And yes, corruption can
> happen even if you have raid, for many many reasons. Detecting means
> knowing when to not trust something, when to go for the backup tapes...
>
> raid is great for protecting against individual disks or sectors going
> bad. But raid, especially high performance implementations, do not
> checksum data or detect corruptions. 
>
> They're different purpose with almost zero overlap in purpose or even
> goal...
>
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>  
Add a salvagable file system to ext4, i.e. when a file is deleted, you 
just rename it and move it to a directory called DELETED.SAV and recycle 
the files as people allocate new ones.  Easy to do (internal "mv" of 
file to another directory) and modification of the allocation bitmaps.  
Very simple and will pay off big.  If you need help designing it, just 
ask me.

Jeff
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