Re: ext4 features (checksums)

Avi Kivity
2006-07-05T12:10:13Z

Bill Davidsen wrote:
>
>
> > Not syncing unused area is possible, if there was a way for raid resync
> > to ask the fs what blocks are not in use. I.e. get the
> > free block list in disk block order. Then raid resync could skip
> those.
> >
> Current RAID code supports having a bitmap of dirty stripes, and can
> just sync those during recovery. I'm sure Neil could explain it better,
> but this is available without worrying about fs type. Now. Today.
>

This is only when the you reconstruct a disk that was once part of the
RAID. If you are adding a brand new disk, all stripes are dirty.

This happens in two scenarios: an unclean RAID shutdown, and when you
have a remote mirror which can be disconnected by network problems.

If the RAID is integrated in the filesystem (or into an object storage
system), you can handle the new disk case too.

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