On Thu, Feb 16 2012 at 11:46pm -0500, Stuart D. Gathman <stuart@bmsi.com> wrote: > Long ago, Nostradamus foresaw that on Feb 16, Mike Snitzer would write: > > >>An elegant part of the LVM system is that the device mapper kernel support is > >>very general, and new data structures can be experimented with entirely in user > >>code - with a script language even. Metadata for experimental structures does > >>not have to stored with the main metadata. > > > >Please note that the dm-thinp code has metadata in the kernel (on-disk > >format for btrees, etc) much like a filesystem would have. So there is > >both kernel and userspace (lvm2) metadata for dm-thinp. > > Yes, but isn't this loaded into the kernel via userland tools like > device-mapper? The 'thin-pool' and 'thin' DM device tables are loaded from userspace via DM interfaces. The kernel metadata isn't loaded from userspace. It is created and/or changed by certain actions taken from userspace (via DM messages). > So while a kernel feature would be required for a new > type of kernel metadata, experimental uses of existing formats can > be done in userland. The kernel manages the kernel's metadata. But the LVM metadata that userspace uses to coordinate and manage the thin devices can be changed independently. The thin-provisioning-tools know the kernel's metadata format and can check it (and in the future repair it). _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
