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Date:      Sun, 7 Mar 2004 21:42:18 +0000
From:      Nik Clayton <nik@freebsd.org>
To:        Nik Clayton <nik@freebsd.org>
Cc:        current@freebsd.org
Subject:    Re: System hangs with vnode backed md(4) devices -- still a problem?
Message-ID:  <20040307214218.GA87623@clan.nothing-going-on.org>
In-Reply-To: <22B16B3E-6D5F-11D8-BDE4-000393863D48@freebsd.org>
References:  <22B16B3E-6D5F-11D8-BDE4-000393863D48@freebsd.org>

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On Wed, Mar 03, 2004 at 10:07:17PM +0000, Nik Clayton wrote:
> Toward the end of last year, through to earlier this year, -current had =
=20
> a problem with vnode backed md(4) devices.  Specifically,
>=20
>     truncate -s 6G foo.md
>     mdconfig -a -t vnode -f foo.md -u 0
>     newfs /dev/md0
>     mount /dev/md0 /mnt
>     rsync /large/amount/of/data /mnt
>=20
> would cause the rsync process to eventually get stuck in a wdrain =20
> state, and other processes in the system would gradually hang -- =20
> processes were still running, but doing anything that might need to =20
> read from a buffer caused the process to hang.  Eventually, everything =
=20
> would be hung.
>=20
> If I'm reading the mailing lists right, this was supposed to be solved =
=20
> here:
>     =20
> http://lists.freebsd.org/pipermail/freebsd-current/2003-November/=20
> 013183.html
>=20
> However, I'm still seeing the problem in -current from Jan 14th.  So =20
> I'm wondering if anyone else is seeing it, and if not, a rough idea of =
=20
> when it was fixed. =20

Following some off-list suggestions, I can report that=20

    mount -o sync /dev/md0 /mnt

solves the "copying large amounts of data will hang" problem.  However,
it replaces it with an "unmounting the md0 device hangs" problem.

N
--=20
FreeBSD: The Power to Serve      http://www.freebsd.org/               (__)
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