[ceph-users] Cannot write to cephfs if some osd's are not available on the client network

Paul Emmerich paul.emmerich at croit.io
Sun Oct 7 07:28:06 PDT 2018


solarflow99 <solarflow99 at gmail.com>:
> now this goes against what I thought I learned about ceph fs.  You should be able to RW to/from all OSDs, how can it be limited to only a single OSD??

Clients only connect to the primary OSD of a PG, so technically an OSD
that isn't the primary of any OSD doesn't have to be reachable by
clients.
That doesn't mean that's a good idea to configure a system like this ;)

Paul


>
> On Sat, Oct 6, 2018 at 4:30 AM Christopher Blum <blum at dorf.rwth-aachen.de> wrote:
>>
>> I wouldn't recommend you pursuit this any further, but if this is the only client that would reside on the same VM as the OSD, one thing you could try is to decrease the primary affinity to 0 [1] for the local OSD .
>> That way that single OSD would never become a primary OSD ;)
>>
>> Disclaimer: This is more like a hack.
>>
>>
>> [1] https://ceph.com/geen-categorie/ceph-primary-affinity/
>>
>> On Fri, Oct 5, 2018 at 10:23 PM Gregory Farnum <gfarnum at redhat.com> wrote:
>>>
>>> On Fri, Oct 5, 2018 at 3:13 AM Marc Roos <M.Roos at f1-outsourcing.eu> wrote:
>>>>
>>>>
>>>>
>>>> I guess then this waiting "quietly" should be looked at again, I am
>>>> having load of 10 on this vm.
>>>>
>>>> [@~]# uptime
>>>>  11:51:58 up 4 days,  1:35,  1 user,  load average: 10.00, 10.01, 10.05
>>>>
>>>> [@~]# uname -a
>>>> Linux smb 3.10.0-862.11.6.el7.x86_64 #1 SMP Tue Aug 14 21:49:04 UTC 2018
>>>> x86_64 x86_64 x86_64 GNU/Linux
>>>>
>>>> [@~]# cat /etc/redhat-release
>>>> CentOS Linux release 7.5.1804 (Core)
>>>>
>>>> [@~]# dmesg
>>>> [348948.927734] libceph: osd23 192.168.10.114:6810 socket closed (con
>>>> state CONNECTING)
>>>> [348957.120090] libceph: osd27 192.168.10.114:6802 socket closed (con
>>>> state CONNECTING)
>>>> [349010.370171] libceph: osd26 192.168.10.114:6806 socket closed (con
>>>> state CONNECTING)
>>>> [349114.822301] libceph: osd24 192.168.10.114:6804 socket closed (con
>>>> state CONNECTING)
>>>> [349141.447330] libceph: osd29 192.168.10.114:6812 socket closed (con
>>>> state CONNECTING)
>>>> [349278.668658] libceph: osd25 192.168.10.114:6800 socket closed (con
>>>> state CONNECTING)
>>>> [349440.467038] libceph: osd28 192.168.10.114:6808 socket closed (con
>>>> state CONNECTING)
>>>> [349465.043957] libceph: osd23 192.168.10.114:6810 socket closed (con
>>>> state CONNECTING)
>>>> [349473.236400] libceph: osd27 192.168.10.114:6802 socket closed (con
>>>> state CONNECTING)
>>>> [349526.486408] libceph: osd26 192.168.10.114:6806 socket closed (con
>>>> state CONNECTING)
>>>> [349630.938498] libceph: osd24 192.168.10.114:6804 socket closed (con
>>>> state CONNECTING)
>>>> [349657.563561] libceph: osd29 192.168.10.114:6812 socket closed (con
>>>> state CONNECTING)
>>>> [349794.784936] libceph: osd25 192.168.10.114:6800 socket closed (con
>>>> state CONNECTING)
>>>> [349956.583300] libceph: osd28 192.168.10.114:6808 socket closed (con
>>>> state CONNECTING)
>>>> [349981.160225] libceph: osd23 192.168.10.114:6810 socket closed (con
>>>> state CONNECTING)
>>>> [349989.352510] libceph: osd27 192.168.10.114:6802 socket closed (con
>>>> state CONNECTING)
>>>
>>>
>>> Looks like in this case the client is spinning trying to establish the network connections it expects to be available. There's not really much else it can do — we expect and require full routing. The monitors are telling the clients that the OSDs are up and available, and it is doing data IO that requires them. So it tries to establish a connection, sees the network fail, and tries again.
>>>
>>> Unfortunately the restricted-network use case you're playing with here is just not supported by Ceph.
>>> -Greg
>>>
>>>>
>>>> ..
>>>> ..
>>>> ..
>>>>
>>>>
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: John Spray [mailto:jspray at redhat.com]
>>>> Sent: donderdag 27 september 2018 11:43
>>>> To: Marc Roos
>>>> Cc: ceph-users at lists.ceph.com
>>>> Subject: Re: [ceph-users] Cannot write to cephfs if some osd's are not
>>>> available on the client network
>>>>
>>>> On Thu, Sep 27, 2018 at 10:16 AM Marc Roos <M.Roos at f1-outsourcing.eu>
>>>> wrote:
>>>> >
>>>> >
>>>> > I have a test cluster and on a osd node I put a vm. The vm is using a
>>>> > macvtap on the client network interface of the osd node. Making access
>>>>
>>>> > to local osd's impossible.
>>>> >
>>>> > the vm of course reports that it cannot access the local osd's. What I
>>>>
>>>> > am getting is:
>>>> >
>>>> > - I cannot reboot this vm normally, need to reset it.
>>>>
>>>> When linux tries to shut down cleanly, part of that is flushing buffers
>>>> from any mounted filesystem back to disk.  If you have a network
>>>> filesystem mounted, and the network is unavailable, that can cause the
>>>> process to block.  You can try forcibly unmounting before rebooting.
>>>>
>>>> > - vm is reporting very high load.
>>>>
>>>> The CPU load part is surprising -- in general Ceph clients should wait
>>>> quietly when blocked, rather than spinning.
>>>>
>>>> > I guess this should not be happening not? Because it should choose an
>>>> > other available osd of the 3x replicated pool and just write the data
>>>> > to that one?
>>>>
>>>> No -- writes always go through the primary OSD for the PG being written
>>>> to.  If an OSD goes down, then another OSD will become the primary.  In
>>>> your case, the primary OSD is not going down, it's just being cut off
>>>> from the client by the network, so the writes are blocking indefinitely.
>>>>
>>>> John
>>>>
>>>> >
>>>> >
>>>> >
>>>> >
>>>> >
>>>> >
>>>> >
>>>> >
>>>> >
>>>> > _______________________________________________
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>>>>
>>>>
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-- 
Paul Emmerich

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