[Fwd: Strange networking behaviour in storage server]
Karli Sjöberg
karli.sjoberg at slu.se
Mon Jun 1 10:18:42 UTC 2015
mån 2015-06-01 klockan 12:11 +0200 skrev Andreas Nilsson:
>
>
> On Mon, Jun 1, 2015 at 11:56 AM, Mehmet Erol Sanliturk
> <m.e.sanliturk at gmail.com> wrote:
>
>
> On Mon, Jun 1, 2015 at 2:02 AM, Karli Sjöberg
> <karli.sjoberg at slu.se> wrote:
> mån 2015-06-01 klockan 10:33 +0200 skrev Andreas
> Nilsson:
> >
> >
> > On Mon, Jun 1, 2015 at 10:14 AM, Karli Sjöberg
> <karli.sjoberg at slu.se>
> > wrote:
> > -------- Vidarebefordrat meddelande --------
> > > Från: Karli Sjöberg <karli.sjoberg at slu.se>
> > > Till: freebsd-fs at freebsd.org
> <freebsd-fs at freebsd.org>
> > > Ämne: Strange networking behaviour in
> storage server
> > > Datum: Mon, 1 Jun 2015 07:49:56 +0000
> > >
> > > Hey!
> > >
> > > So we have this ZFS storage server
> upgraded from 9.3-RELEASE
> > to
> > > 10.1-STABLE to overcome not being able to
> 1) use SSD drives
> > as
> > > L2ARC[1]
> > > and 2) not being able to hotswap SATA
> drives[2].
> > >
> > > After the upgrade we´ve noticed a very odd
> networking
> > behaviour, it
> > > sends/receives full speed for a while,
> then there is a
> > couple of
> > > minutes
> > > of complete silence where even terminal
> commands like an
> > "ls" just
> > > waits
> > > until they are executed and then it starts
> sending full
> > speed again. I
> > > ´ve linked to a screenshot showing this
> send and pause
> > behaviour. The
> > > blue line is the total, green is SMB and
> turquoise is NFS
> > over jumbo
> > > frames. It behaves this way regardless of
> the protocol.
> > >
> > > http://oi62.tinypic.com/33xvjb6.jpg
> > >
> > > The problem is that these pauses can
> sometimes be so long
> > that
> > > connections drop. Like someone is copying
> files over SMB or
> > iSCSI and
> > > suddenly they get an error message saying
> that the transfer
> > failed and
> > > they have to start over with the file(s).
> That´s horrible!
> > >
> > > So far NFS has proven to be the most
> resillient, it´s stupid
> > simple
> > > nature just waits and resumes transfer
> when pause is over.
> > Kudus for
> > > that.
> > >
> > > The server is driven by a Supermicro
> X9SRL-F, a Xeon 1620v2
> > and 64GB
> > > ECC
> > > RAM. The hardware has been ruled out, we
> happened to have a
> > identical
> > > MB
> > > and CPU lying around and that didn´t
> improve things. We have
> > also
> > > installed a Intel PRO 100/1000 Quad-port
> ethernet adapter to
> > test if
> > > that would change things, but it hasn´t,
> it still behaves
> > this way.
> > >
> > > The two built-in NIC's are Intel 82574L
> and the Quad-port
> > NIC's are
> > > Intel 82571EB, so both em(4) driven. I
> happen to know that
> > the em
> > > driver
> > > has updated between 9.3 and 10.1. Perhaps
> that is to blame,
> > but I have
> > > no idea.
> > >
> > > Is there anyone that can make sense of
> this?
> > >
> > > [1]:
> > >
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=197164
> > >
> > > [2]:
> > >
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=191348
> > >
> > > /K
> > >
> > >
> >
> >
> > Another observation I´ve made is that during
> these pauses, the
> > entire
> > system is put on hold, even ZFS scrub stops
> and then resumes
> > after a
> > while. Looking in top, the system is
> completly idle.
> >
> > Normally during scrub, the kernel eats
> 20-30% CPU, but during
> > a pause,
> > even the [kernel] goes down to 0.00%. Makes
> me think the
> > networking has
> > nothing to do with it.
> >
> > What´s then to blame? ZFS?
> >
> > /K
> >
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> >
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> >
> >
> > Hello,
> >
> >
> > does this happen when clients are only reading from
> server?
>
> Yes it happens when clients are only reading from the
> server.
>
> > Otherwise I would suspect that it could be caused by
> ZFS writing out a
> > large chunck of data sitting in its caches, and
> until that is complete
> > I/O is stalled.
>
> That´s what so strange, we have three more systems set
> up about the same
> size and none of others are acting this way.
>
> The only thing I can think of that differs that we
> haven´t tested ruling
> out yet is ctld, the other systems are still running
> istgt as their
> iSCSI daemon.
>
> /K
>
> What does a zpool status say? Could very well be disks starting to
> fail.
>
>
> Anything in dmesg concerning cam timeouts?
>
>
> Best regards
>
> Andreas
>
Pool status is fine, scrubbed multiple times without errors. No storage
related errors, we´re using LSI HBA's so no cam, but nothing mps-related
either.
/K
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