Re: [ovirt-users] very very bad iscsi performance

[Philip Brown]

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