On Mon, Dec 18, 2017 at 9:24 AM, 13605702596@xxxxxxx
<13605702596@xxxxxxx> wrote:
> hi John
>
> thanks for your answer.
>
> in normal condition, i can run "ceph mds fiail" before reboot.
> but if the host reboots by itself for some reason, i can do nothing!
> if this happens, data must be losed.
>
> so, is there any other way to stop data from being losed?
>
no data get lost in this condition. just IO stall for a few seconds
> thanks
>
> ________________________________
> 13605702596@xxxxxxx
>
>
> From: John Spray
> Date: 2017-12-15 18:08
> To: 13605702596@xxxxxxx
> CC: ceph-users
> Subject: Re: cephfs miss data for 15s when master mds rebooting
> On Fri, Dec 15, 2017 at 1:45 AM, 13605702596@xxxxxxx
> <13605702596@xxxxxxx> wrote:
>> hi
>>
>> i used 3 nodes to deploy mds (each node also has mon on it)
>>
>> my config:
>> [mds.ceph-node-10-101-4-17]
>> mds_standby_replay = true
>> mds_standby_for_rank = 0
>>
>> [mds.ceph-node-10-101-4-21]
>> mds_standby_replay = true
>> mds_standby_for_rank = 0
>>
>> [mds.ceph-node-10-101-4-22]
>> mds_standby_replay = true
>> mds_standby_for_rank = 0
>>
>> the mds stat:
>> e29: 1/1/1 up {0=ceph-node-10-101-4-22=up:active}, 1 up:standby-replay, 1
>> up:standby
>>
>> i mount the cephfs on the ceph client, and run the test script to write
>> data
>> into file under the cephfs dir,
>> when i reboot the master mds, and i found the data is not written into the
>> file.
>> after 15 seconds, data can be written into the file again
>>
>> so my question is:
>> is this normal when reboot the master mds?
>> when will the up:standby-replay mds take over the the cephfs?
>
> The standby takes over after the active daemon has not reported to the
> monitors for `mds_beacon_grace` seconds, which as you have noticed is
> 15s by default.
>
> If you know you are rebooting something, you can pre-empt the timeout
> mechanism by using "ceph mds fail" on the active daemon, to cause
> another to take over right away.
>
> John
>
>> thanks
>>
>> ________________________________
>> 13605702596@xxxxxxx
>>
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>> ceph-users@xxxxxxxxxxxxxx
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>>
>
>
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