On 2005-02-15T20:17:10, shahid shaikh <shahid.shaikh@xxxxxxxxx> wrote: Sorry about this late reply, but I just stumbled across this post. To recap, the issue is that we want to prevent LVM2/EVMS2 etc from scanning (and using!) the raw physical devices if those are already claimed/used by multipath. LVM2 has a special handling for md_component_detection already; what I want to propose in the following is a bit more general, and I've discussed it with Hannes before. Problem: A general solution for finding out whether another component is using the device we're looking at. Proposed solution: Introduce sub-devices into the sysfs tree. (And, automatically, backlink those to parent devices, but that's just so the tree can be traversed in any order.) For example, /sys/block/sda would have a sub/ directory with "dm-0" in there, pointing at /sys/block/dm-0 (surprise). The /sys/block/dm-0/parent/sd{a,b} entries would do a very surprising thing. This would also allow us to handle partitions in DM better: as all linear mappings on top of /dev/dm-0 would show up in block/dm-0/sub/ and vice versa. md could work the same: block/sys/md0/parent/ would list all the devices (or partitions) which it consists of. This very simple(?) change would make a number of things much easier to figure out. Caveats: - This obviously only works if the devices are already active, not if the specific user is offline; if LVM2 scans before multipath-tools has worked its magic, it won't work. (But then, multipath-tools can figure out that there's already someone else using the raw physical device and not mess with it! Woho, world saved!) - This ONLY exports very rudimentary hierarchical information; it won't tell you what the device is used for or how. However, that information alone would be very helpful already. Greg, Alasdair? List? Sincerely, Lars Marowsky-Brée <lmb@xxxxxxx> -- High Availability & Clustering SUSE Labs, Research and Development SUSE LINUX Products GmbH - A Novell Business