Hello, I have just been making some snapshot performance benchmarks on a Debian Etch system. Kernel: 2.6.18-4-686 (2.6.18.dfsg.1-12etch1) dmsetup: 1.02.08-1 lvm2: 2.02.06-4 I have been using commands of the form: time dd if=/dev/zero of=/dev/volgroup/test bs=1M count=100 to get speeds for copying to a LVM device both WITH and WITHOUT a single snapshot. It seems that writes take >=10 times longer the first time a newly snapshot origin device is written to. I was expecting somthing like a 2x or 3x performance loss as 1 physical read and 2 physical writes must occur for a single logical write. I was NOT expecting there to be a 10x overhead. As I move to larger devices (bs=1M count=1000) the 10x figure rises to nearer 20x. This is also true on mounted origin LV's. Has anyone else benchmarked this? Is this normal? Thanks for any feedback Alex Owen _______________________________________________ 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/
