Virtual size lets you create a 200G file system om a 20G LV and then lvextend as needed, without the need to resize the filesystem. Read about sparse files for ideas of other uses. It'd like a sparse device in that blocks need not actually exist until they are written to. It currently has a performance and flexibility impact that prevents us from using it, though we would like to. "Linda A. Walsh" <lvm@tlinx.org> wrote: >I just saw it in the man page, and first thing I tried was creating a >logical volume >by just giving a --virtualsize, arg -- thinking it would 'auto-extend >it' as needed. > >Nep. > >Next was looking on the net and seeing an example that gave it some >small size (-L 1G), >with a virtual size of 2G. So what is that supposed to do? > >I just now thought to copy a bunch of files ( that differed from >yesterday to today) to a tmp >partition) but had it fail miserably when it REALLY failed upon >reaching >the physical >limit -- not the virtual limit!).... > > >I was trying to use rsync to copy from a snap from yesturday of /home >that was mounted on >/ohome to 'home.diff' (the partition that I used 'virtual size' with, >... I gave it a real >size of 1G, and a virtual size of 1T. > >Using rsync, I had --compare-dest=/ohome (where I mount yesturday's >snap) and copied >from /home to /home.diff (the virtual partition).... Well the diffs >were > 1G, so had >hoped /home.diff would expand to it's virtual size... Anyway, got I/O >errors, after I >ran out of space. Ok, so *that*'s not what virtual size is >for...either! > >Anyway, I unmounted the now 'corrupt' /home.diff, and tried to remove >it... >Got all sorts of i/o errors using lvremove Home.diff. (-f didn't work >either). > >Got it to remove with lvremove -f /dev/PV/Home.diff >That gave I/O errors too, but successfully completed... > >So what's virtual size good for, anyway? > > > >_______________________________________________ >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/ -- Sent from my Android phone with K-9 Mail. Please excuse my brevity. _______________________________________________ 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/
