On Sat, 26 Mar 2011 00:24:56 -0400 (EDT) "Stuart D. Gathman" <stuart@bmsi.com> wrote: > Assuming my theory is correct, the morals would be: ... > 2) make sure important LVs do not span multiple PVs (except for LVM > mirroring) - you could be unhappy in the event of a system crash. I don't believe that multiple PVs necesarily makes a difference. On a single PV, there is no guarantee that writes make it to disk during a power failure, what order they make it in, or even if a write is correct while voltage is dropping. The drive itself could reorder a write (NCQ), the raid card could do so, etc. One might say the moral of the story is "don't run important production servers on spotty power systems without an effective UPS". Someone mentioned journaling. Journaling does not of course guarantee data consistency, only makes meta data, more likely to be consistent, so regardless when you undervolt a drive during power failure something is subject to go wrong, aside from the more obvious effects of even an instant power cut while writing a block. Moral - don't yank the power is the data is important. -- Ray Morris support@bettercgi.com Strongbox - The next generation in site security: http://www.bettercgi.com/strongbox/ Throttlebox - Intelligent Bandwidth Control http://www.bettercgi.com/throttlebox/ Strongbox / Throttlebox affiliate program: http://www.bettercgi.com/affiliates/user/register.php _______________________________________________ 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/
