This is still causing me headaches... Does anybody have any insight on this? --- bowmailtmp-lvm@yahoo.com wrote: > ok, i think i've got an idea what's going on here, > it > seems that the lvm cache may be the problem here. > it > seems like in some cases if i wait a couple > *minutes* > then the data magically shows up in the proper > physical sectors of the disk. in some cases it is > faster, some quite slow. can someone confirm this > for > me and give me an idea of the mechanics involved > with > the cache? also, is there a command to force the > cache to be flushed out? i'll keep looking through > the man pages for this. > > thanks, > dave > > --- bowmailtmp-lvm@yahoo.com wrote: > > I have been having a very difficult time > correlating > > physical addresses to LVM2/DM addresses. > > > > for instance, if i do: > > dmsetup table /dev/mapper/avtest-vdisk2g > > > > the result is: > > 0 4194304 linear 22:65 384 > > > > from what i currently understand, this means > logical > > extent 0 (which is composed of 8192 512 byte > sectors > > in the default config) of this LV should start at > > physical sector 384 of device 22:65 (/dev/hdd1 on > my > > machine) > > > > after i've written to the logical device a couple > > times, it appears this correlation doesn't hold > when > > i > > access the physical sectors on hdd1 using dd. > > however, if i use dd to access the sectors through > > the > > LV, all the data appears as it should. i was > under > > the impression that the logical to physical > mappings > > was quite straightforward and intuitive, but i > feel > > that i am missing some key information. Can > someone > > help me out of is there decent developer > > documentation > > somewhere that explains the mappings? > > > > As a more complete example of my problem, if i do > > the > > following: > > > > dd if=/dev/zero of=/dev/avtest/vdisk2g count=1 > > then do: > > dd if=/dev/avtest/vdisk2g of=tmpfile.out count=1 > > then tmpfile.out contains 512 bytes of zeros. > > > > however, if I do: > > dd if=/dev/hdd1 of=tmpfile.out skip=384 count=1 > > then tmpfile.out contains other data, not the > zero's > > i > > would expect from the output of the dmsetup table > > command above. I feel i'm missing something > fairly > > basic here, but I haven't had any luck tracking > this > > relationship down. I suppose there is always the > > sourc code :) > > > > > > Thanks a lot. > > > > > > > > _______________________________________________ > > 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/ > > > > _______________________________________________ > 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/ > _______________________________________________ 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/
