FYI, I just tried it with direct lun. it is as bad or worse. I dont know about that sg io vs qemu initiator, but here is the results. 15223: 62.824: IO Summary: 83751 ops, 1387.166 ops/s, (699/681 r/w), 2.7mb/s, 619us cpu/op, 281.4ms latency 15761: 62.268: IO Summary: 77610 ops, 1287.908 ops/s, (649/632 r/w), 2.5mb/s, 686us cpu/op, 283.0ms latency 16397: 61.812: IO Summary: 94065 ops, 1563.781 ops/s, (806/750 r/w), 3.0mb/s, 894us cpu/op, 217.3ms latency ----- Original Message ----- From: "Paolo Bonzini" <pbonzini@redhat.com> To: "Nir Soffer" <nsoffer@redhat.com> Cc: "Philip Brown" <pbrown@medata.com>, "users" <users@ovirt.org>, "qemu-block" <qemu-block@nongnu.org>, "Stefan Hajnoczi" <stefanha@redhat.com>, "Sergio Lopez Pascual" <slp@redhat.com>, "Mordechai Lehrer" <mlehrer@redhat.com> Sent: Monday, July 20, 2020 3:46:39 PM Subject: Re: [ovirt-users] very very bad iscsi performance Il lun 20 lug 2020, 23:42 Nir Soffer <nsoffer@redhat.com> ha scritto:
I think you will get the best performance using direct LUN.
Is direct LUN using the QEMU iSCSI initiator, or SG_IO, and if so is it using /dev/sg or has that been fixed? SG_IO is definitely not going to be the fastest, especially with /dev/sg. Storage
domain is best if you want to use features provided by storage domain. If your important feature is performance, you want to connect the storage in the most direct way to your VM.
Agreed but you want a virtio-blk device, not SG_IO; direct LUN with SG_IO is only recommended if you want to do clustering and other stuff that requires SCSI-level access. Paolo