Re: ext4 features (checksums)

Jeff Garzik
2006-07-04T01:04:17Z

Neil Brown wrote:
> Can't say I agree with this layering distinction.
> It's been some years that I've felt that most 'logical volume
> management' really belongs in the filesystem.
> Why have a dm that chops devices up in to segments and assembles them to
> look like a big device, only to have that big device chopped up and
> presented as files. Seems like double handling to me.

Agreed, and allow me to take an even more radical position:

I've long felt that things like snapshotting and mirroring made a lot of
sense at the filesystem level -- as do layered filesystems, just like we
layer block devices.

Block device drivers (MD, DM) get ever more complicated, and ultimately
become mini-filesystems themselves. The metadata managed by blkdev
drivers continues to increase in complexity. What is represented to the
upper layer as a contiguous run of bytes is really, under the hood,
chunks of data coalesced logically -- just like files in a filesystem.

The more complex that blkdev drivers become, the more and more they will
look like filesystems.

Jeff