On 06/17/10 04:23, Zdenek Kabelac wrote: > Dne 16.6.2010 21:27, Takahiro Yasui napsal(a): >> On 06/16/10 05:30, Zdenek Kabelac wrote: >>> Dne 16.6.2010 02:34, Phillip Susi napsal(a): >>>> On 06/15/2010 04:41 PM, Takahiro Yasui wrote: >> ... >>>> What if I don't want ANY devices to be scanned every time an lvm command >>>> is run? Shouldn't they be scanned once when udev first detects they >>>> have been attached, and no more? I thought removing /dev from the scan= >>>> line would do that, but it didn't. >>>> ... >> It is helpful if udev can handle this issue, but I'm wondering how it can >> do it. > > I'm not working on this part, but AFAIK, once we could start 'trust' udev, we > can keep persistent cache aware of any changes that might have happened to > devices listed in metadata. Implementation details are still 'moving topic'. > > Obviously you can not skip write/update access to metadata areas, but it > should be possible to avoid scanning for 'read-only' data access. Thank you for your explanation. Yes, I agree that it is possible to avoid scanning for 'read-only' data access, but I also believe it is possible for 'write' adata access. > Also there is another thing in progress - metadata-balance code - where you > essentially do not need to read/write metadata from/to every PV in VG - but > just on reasonable safe amount of them - i.e. 5 from 100 of PVs - the rest of > them is marked invisible (different from pvcreate --metadatasize 0) AFAIK, metadata-balance feature would reduce the number of disk accesses, but I believe that the goal is to access PVs related to the VG which lvm command is going to manipulate. Introducing metadata cache feature on disk or a kind of daemon managing all metadatas, or using /etc/lvm/backup could be solution. I hope we could continue discussing this topic on lvm-devel? Thanks, Taka _______________________________________________ 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/
