What is the underlying disk hardware you are running this on? virtual, spinning, ssd, nvme?
On Thu, Oct 13, 2022 at 2:01 AM Pawan Sharma <sharmapa...@microsoft.com> wrote: > > adding this to lvm-devel mailing list also. > > Regards, > Pawan > ________________________________ > From: Pawan Sharma > Sent: Wednesday, October 12, 2022 10:42 PM > To: linux-lvm@redhat.com <linux-lvm@redhat.com> > Cc: Mitta Sai Chaithanya <mit...@microsoft.com>; Kapil Upadhayay > <kupadha...@microsoft.com> > Subject: LVM2 : performance drop even after deleting the snapshot > > Hi Everyone, > > > We are evaluating lvm2 snapshots and doing performance testing on it. This is > what we are doing : > > dump some data to lvm2 volume (using fio) > take the snapshot > delete the snapshot (no IOs anywhere after creating the snapshot) > run the fio on lvm2 volume > > Here as you can see, we are just creating the snapshot and immediately > deleting it. There are no IOs to the main volume or anywhere. When we run the > fio after this (step 4) and we see around 50% drop in performance with > reference to the number we get in step 1. > > It is expected to see a performance drop if there is a snapshot because of > the COW. But here we deleted the snapshot, and it is not referring to any > data also. We should not see any performance drop here. > > Could someone please help me understand this behavior. Why are we seeing the > performance drop in this case? It seems like we deleted the snapshot but > still it is not deleted, and we are paying the COW penalty. > > System Info: > > OS : ubuntu 18.04 > Kernel : 5.4.0 > > # lvm version > LVM version: 2.02.176(2) (2017-11-03) > Library version: 1.02.145 (2017-11-03) > Driver version: 4.41.0 > > We also tried on latest ubuntu with newer version of LVM. We got the same > behavior. > > Any help/pointers would be appreciated. Thanks in advance. > > Regards, > Pawan > _______________________________________________ > linux-lvm mailing list > linux-lvm@redhat.com > https://listman.redhat.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://listman.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
