Date: Tue, 23 Jun 2015 17:14:13 -0700 From: John-Mark Gurney <jmg@funkthat.com> To: Max Gurtovoy <maxg@mellanox.com> Cc: freebsd-scsi@freebsd.org, Sagi Grimberg <sagig@mellanox.com>, Oren Duer <oren@mellanox.com>, Hans Petter Selasky <hanss@mellanox.com>, mav@freebsd.org Subject: Re: gmultipath HA over iscsi/iser Message-ID: <20150624001412.GS96349@funkthat.com> In-Reply-To: <55897E4B.8060608@mellanox.com> References: <557DA8C0.1020209@mellanox.com> <20150619162015.GD96349@funkthat.com> <55897E4B.8060608@mellanox.com>
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Max Gurtovoy wrote this message on Tue, Jun 23, 2015 at 18:42 +0300: > On 6/19/2015 7:20 PM, John-Mark Gurney wrote: > > Max Gurtovoy wrote this message on Sun, Jun 14, 2015 at 19:16 +0300: > >> lately I was testing HA using gmultipath utility over iSCSI/iSER devices. > >> I'm working on 11-current code base. > >> I created 1 LUN on the target side and connected via 2 different > >> physical ports from the initiator side. > >> On the initiator side I see see /dev/da0 and /dev/da1. > >> I created multipath device using: > >> gmultipath label dm0 /dev/da0 /dev/da1. > >> Now I have new device /dev/multipath/dm0. > >> I set kern.iscsi.fail_on_disconnection=1 (to fail IO fast). > >> > >> Issue 1: > >> ------------- > >> I can't run simple fio/dd traffice over /dev/da0 nor /dev/da1. > >> The only traffic that possible is using the multipath device dm0. > >> Is this by design ? > > > > This is probably because geom only lets one writer open the device at > > a time, and when the dm0 device is open, it blocks any other writers > > to it's underlying devices... There is a special geom debug flag that > > you can set to avoid this... > > I tried this debug exclusive flag with iSCSI/iSER but when I set it to 0 > the system crushed at the 'gmultipath label ...' stage. > John, > did you try it over iSCSI ? Nope, I didn't.. In fact, I was thinking of another debug flag the one in kern.geom.debugflags, but that one should have worked too... Since it doesn't, please file a bug report and notify the maintainer of multipath with a complete report... > >> In the linux implementation we can run traffic on both block devices and > >> multipath devices. > >> > >> Issue 2: > >> -------------- > >> I run some fio traffic utility over multipath device dm0 on initiator > >> side with port toggling in a loop > >> > >> Port 1 down --> sleep 2 mins (iSCSI/ISER device reconnecting meanwhile > >> with no success) --> port 1 up --> sleep 5 mins (iSCSI/ISER device > >> reconnecting successecfully) > >> Port 2 down --> sleep 2 mins (iSCSI/ISER device reconnecting meanwhile > >> with no success) --> port 2 up --> sleep 5 mins (iSCSI/ISER device > >> reconnecting successecfully) > >> > >> The expected result is that when the port N is down than the traffic > >> moves to the available port and continue succesfully. > >> I run this test for many hours and traffic FAILED (even though there was > >> at least 1 suitable path between initiator and target). > > > > Someone else will need to answer this one... > > I'm pretty new in the FreeBSD community so I don't know who is the > maintainer of the gmultipath driver. Though I realize it's difficult, it's easiest to look at the source to see who's been touching it last: https://svnweb.freebsd.org/base/head/sys/geom/multipath/g_multipath.c?view=log Looks like mav has been somewhat active recently... I've cc'd him... > Maybe we can discuss about testing the gmultipath driver over iscsi/iser > devices and fix some bugs together ? I can help out some, but engaging mav, or some of the others that are more active in storage would be better... > We are planning to add it to our test plan and HA is in high priority > for us. You should definately talk/coordinate w/ the people at iXsystems (mav works there), as they work in storage w/ iSCSI, etc. -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."
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