Hi, for an application I am just working on it looks like lvm snapshots would be just what I need as far as functionality is concerned. Unfortunately, I am experiencing such a massive degradation in performance, that the result is almost useless. I'm working on a fairly fast machine (Quadcore, 8GB RAM) with a big hardware RAID array and lvm2 (Debian Lenny; Linux 2.6.26-1-amd64; LVM version:2.02.39 (2008-06-27) Library version: 1.02.27 (2008-06-25) Driver version: 4.13.0) Sequentially writing to a file (ext3) on a logical volume, I get a sustained performance of ~ 250 MB/sec. When I create a snapshot volume, the write throughput drops to 7-8 MB/secs (on the original volume; writing to the snapshot I see a significant degradation, but not nearly, as bad; read performance is o.k.).Is this "normal" or is there anything I can do to about it? I looked in this list and searched the WWW but couldn't find any concrete information on the performance impact of snapshots (except http://www.nikhef.nl/~dennisvd/lvmcrap.html). It seems like write performance should probably be less then 1/3 of the original throughput, because every write to the source volume causes 3 I/O operations plus some overhead for meta data. More difficult to estimate would be the time lost by additional head movements. Still, a throughput degradation by a factor of 30 seems pretty extreme. Any ideas? Regards, Peter Daum _______________________________________________ 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/
