Re: Notes on support for multiple devices for a single filesystem

Jeff Garzik
2008-12-17T21:27:58Z

Kay Sievers wrote:
> Features like the very nice and useful directory-based snapshots would
> also not be possible with simple block-based multi-devices, right?

Snapshotting via block device has always been an incredibly dumb hack,
existing primarily because filesystem-based snapshots did not exist for
the filesystem in question.

Snapshots are better at the filesystem level because the filesystem is
the only entity that knows when the filesystem is quiescent and
snapshot-able.

ISTR we had to add ->write_super_lockfs() to hack in support for LVM in
this manner, rather than doing it the right way.

Jeff