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Date:      Fri, 5 Aug 2016 09:03:40 -0600
From:      Alan Somers <asomers@freebsd.org>
To:        Daniel Genis <daniel.genis@gmx.de>
Cc:        Alan Somers <asomers@freebsd.org>, FreeBSD <freebsd-stable@freebsd.org>
Subject:   Re: zfs recv causes nfs server to throw NFSERR_IO i/o errors
Message-ID:  <CAOtMX2gqKHBEQB-xL5jjdRmO4x6bM4ND%2B0Ndc%2B_mRaiiqrMZfA@mail.gmail.com>
In-Reply-To: <1eb419ed-4180-11c2-3bf3-5d3013a07197@gmx.de>
References:  <1df33129-0c3e-dfc3-6867-46ab0473ae57@gmx.de> <CAOtMX2j2DRNW87XypXNDs17e838EhPtUhX2OZJq2X5QSOb731A@mail.gmail.com> <1eb419ed-4180-11c2-3bf3-5d3013a07197@gmx.de>

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Glad to help.  BTW, that setting is the default in FreeBSD 11.

On Fri, Aug 5, 2016 at 8:54 AM, Daniel Genis <daniel.genis@gmx.de> wrote:
> Thank you, that probably is what the doctor ordered!
> My quick testing shows that it's very likely fixed. Kudos! :-)
>
> On 08/05/2016 04:11 PM, Alan Somers wrote:
>> On Fri, Aug 5, 2016 at 7:22 AM, Daniel Genis <daniel.genis@gmx.de> wrote:
>>> Hi everyone,
>>>
>>> we've been tracing an issue where snapshot replication is causing
>>> interruptions for the NFS serivce.
>>>
>>> The problem is as follows:
>>>
>>> Every time a zfs recv finishes, there is a chance for the NFS server to
>>> return an NFSERR_IO for a GETATTR call. This shows up as input/output
>>> errors on the nfs clients.
>>>
>>> Here the tcpdump showing the NFS conversation:
>>> https://nopaste.me/view/95d1a79d
>>>
>>> NFS 202 V3 GETATTR Call (Reply In 6043), FH: 0x8c711a60
>>> NFS 98  V3 GETATTR Reply (Call In 6042) Error: NFS3ERR_IO
>>> NFS 222 V3 LOOKUP Call (Reply In 6046), DH: 0x6694634f/example.file.txt
>>> NFS 102 V3 LOOKUP Reply (Call In 6045) Error: NFS3ERR_ACCES
>>>
>>> We've been able to verify that there is a _direct_ correlation between
>>> the zfs recv command and these NFS errors. For every input/output error
>>> we can find a log entry of a replication just finishing (zfs recv exiting).
>>>
>>> The receiving server is running 10.3-RELEASE
>>>
>>> I've read about a VFS/ZFS deadlock issue which is to be included/fixed
>>> in Freebsd 11.0-BETA4.
>>>
>>> Could our issue be related?
>>> Otherwise does anyone have any suggestions how to tackle this issue?
>>>
>>>
>>> For the record, say we have two volumes:
>>> tank/volumeA and tank/volumeB
>>>
>>> If there is a zfs recv busy for tank/volumeA then tank/volumeB can get
>>> these NFS "io" errors, it does not have to be the same volume.
>>>
>>>
>>> Has anyone else seen/experience this as well?
>>>
>>> Any insights are appreciated!
>>>
>>> With kind regards,
>>>
>>> Daniel
>> Try adding mountd_flags="-S" to /etc/rc.conf.
>
>



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