On Wed, Apr 02, 2003 at 08:47:04AM -0800, Aman Shahi wrote: > > does that mean that I will have to dedicate that > physical device for the Snapshot. I mean if I had > 4 device /dev/sda /dev/sdb /dev/sdc /dev/sdd and > previously if I was striping my original LV over > all the 4 devices, in the current context I stripe > the original LV over 3 devices and create the > Snapshot LV over the 4th (dev/sdd) ? Not at all. the LV will take up only as much space on that PV as you allocate to it. All that is happening by adding the device name to the end of command is that LVM is forced to use only that device when allocating the volume, rather than being allowed to use any device in the Volume Group. Whether it affects the performance of other devices on the system is up to you and how you have spread the load across devices. Personally I allocate performance-critical filesystems on seperate disks and low-use filesystems I leave to LVM to allocate. Of course if the load changes you can always use pvmove to change where the data is located. In the case of 4 disks with 4 stripes (ie there is no "spare" disk) I think what I would do would be to allocate a striped snapshot LV so that at least the COW load is also spread evenly across all the disks. None of this is mandatory, you are free to allocate LVs where you like (that's the point of LVM) and performance matters are very much specific to the particular installation. patrick _______________________________________________ linux-lvm mailing list linux-lvm@sistina.com http://lists.sistina.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
